The Human Fossil Record


#The Nature of Transitional Fossils

Some time ago, the Discovery Institute’s Casey Luskin commented on the human origins exhibit at the Smithsonian Institution, suggesting that palaeoanthropologists use evolutionary theory to describe the progression of the human lineage even when they don’t have transitional fossils with which to work. He writes:

What’s ironic, however, is that if you ask the question How Do We Know Humans Evolved? the answer you’re given is, “Fossils like the ones shown in our Human Fossils Gallery provide evidence that modern humans evolved from earlier humans.” So whether you find fossils or you don’t, that’s evidence for evolution.

Indeed, it has become an article of faith for those espousing both the young earth creation (hereafter YEC) model and many who hold to the intelligent design model that transitional fossils do not exist and therefore evolution has not taken place. Support for this position usually entails attacking the weak areas of the fossil record, where burial processes have left us little with which to work, or the creation of straw men arguments in which transitional fossils are defined in such a way that none could ever be found. Often this centers on the concept of “missing link,” a term that is habitually used in the popular press and young earth creation and intelligent design literature when referring to fossil remains but which has little to no meaning for biologists or palaeontologists. As Ahlberg and Clack (Ahlberg and Clack 2006) write:

But the concept has become freighted with unfounded notions of evolutionary ‘progress’ and with a mistaken emphasis on the single intermediate fossil as the key to understanding evolutionary transitions. Much of the importance of transitional fossils actually lies in how they resemble and differ from their nearest neighbours in the phylogenetic tree, and in the picture of change that emerges from this pattern.

Contrary to common misconceptions, the fossil record does not record one single lineage for any family of organisms but rather a series of branches, with many related species coexisting synchronously. Darwin hypothesized that the evolutionary record reflected this bushiness and drew such a diagram in his journal. At the time, though, he had little in the way of fossil evidence to back up this position. Much has changed since his day.

An analogy for understanding this “bushiness” was best described by Prothero and Buell (Prothero and Buell 2007). They suggest that the reader consider his or her own genealogy. You and your siblings are the direct descendents of your parents and, while you are similar to them, each of you has different characteristics not shared with them as well as characteristics that you do share. Your parents have siblings as well (your aunts and uncles), and your grandparents are their last common ancestors. These siblings have their own children (your cousins), who have different and similar traits relative to their parents. They are broadly recognizable as being related to you (“oh, I see you have Aunt Edna’s nose”) but three or four generations out, they will become less and less so. These are the “nearest neighbours” that Ahlberg and Clack describe. In this analogy, each of these cousins represents a transitional form from what was (your grandparents) to what will be down the road.

For example, no one would confuse a frog with a salamander but if you trace the fossil record of each back in time, eventually you encounter a fossil, Gerobatrachus hottoni which was recently discovered (Anderson et al. 2008) that is best described as a “frogamander,” having the basal characteristics of both frogs and salamanders. Had we seen such an animal at the time, it is likely we would not have found it remarkable because it would have resembled the species around it. One lineage eventually diverged into frogs, salamanders and other amphibians. Most (just like Darwin proposed in his tree diagram with the little hatch marks at the tip of many branches) went extinct.

Taxonomy and the Beginnings of Human Origins

All life is classified based on a system devised by Carolus Linneaus in 1735 in his remarkable work Systema Naturae. This system gives all recognized species an individual place based on a system of hierarchy. The study of classification is known as taxonomy. A taxonomic ranking for humans would be this:

When a fossil is excavated, the first thing that the palaeontologist does is make a taxonomic assessment of where it fits in a sequence of known fossils. Traits that are shared with other like species or genera are referred to as primitive traits. Examples of this in humans are five fingers and the presence of three arm bones. We share this with all mammals. Traits that are new or are not shared with other like species are referred to as derived traits. Examples of this in humans are the skeletal changes in the pelvis and the foot to allow for walking upright. We do not share these with any other primates.

Transitional fossils in the human fossil record are distinguished at both the genus and species level. This group includes the extinct genera Ardipithecus and Australopithecus and the current genus Homo. All species exceptHomo sapiens are extinct. Much of the recent study of early humans focuses on the transition from Ardipithecus(‘Ardi’) to Australopithecus(‘Lucy’ and similar fossils) and from Australopithecus to Homo, the genus that led eventually to us. While each of the australopithecine species identified in the fossil record has derived characteristics that separate them from their ancestors and from each other, only one led to the genus Homo.

In future posts, I will describe the evidence for human evolution and why this evidence is compelling. It suggests that we have had a long, varied history filled with great leaps of change, crushing defeat, and eventual expansion into all areas of the globe.

#Bipedality

One of the most fruitful and exciting areas of research in palaeoanthropology is the search for the last common ancestor to the higher apes and humans. This question is inextricably tied to concepts of what separates humanity from the animals around us. This is a question that has spiritual as well as physical ramifications. In this set of posts, we are dealing with what makes us human from a biophysical perspective.

Traditionally, paleoanthropologists have considered the hallmark of humanity to be habitual bipedalism. While we share many characteristics in common with the higher apes, this trait alone is practiced by no other animal. Some animals practice facultative bipedalism, allowing them to go short distances on two legs when necessary, but only humans use it as their only form of locomotion. Put a man on all fours and even a squirrel can outrun him. Bipedalism is a skill that we learn early in life, before we are sentient and even understand what makes us different from the animals around us. It is programmed into us.

Bipedalism is marked by a number of anatomical modifications to the standard primate body. These center on the pelvis and involve changes in the head (cranium) and the rest of the body (postcranium), reflecting a shifting of the center of balance from the abdominal cavity to the hip. In mammals, the hip is composed of three mirrored sets of bones: the ilium, the ischium and the pubis (Figure 1). The top part of the leg fits into the bottom-rear portion of the ilium, into a round socket called the acetabulum. It is one of two ball-and-socket joints in the body, the other being where the arm fits into the scapula at the top of your shoulder.

Where the two pubis bones fit together in the front and the two ilia meet in the back with the sacrum forms the birth canal. In chimpanzees and gorillas, the ilium is narrow and tall (Figure 2). Consequently, the connection to the upper leg bone, the femur, is straight up and down. In humans, the ilium is flat and flared, creating an outward bowing of the top of the femur, which allows for the balance necessary for walking upright (see Figure 1). This, in turn, creates what is known as the valgus knee, where the bottom of the femur meets the top of the large lower leg bone, the tibia, at an angle. The fact that the two bones meet at an angle provides for a better balance of the body mass for upright walking. In contrast, when higher apes such as gorillas and chimpanzees stand, the femur and the tibia are both perpendicular to the ground, resulting in a straight knee joint. Consequently, when chimpanzees walk upright, they swing side to side in an ungainly fashion to simulate the balance that is inherent in human walking.

Other changes are present above the hip, as well. Because they are quadrupedal, chimpanzees, gorillas and orangutans have a straight backbone, or vertebral column (Figure 3). In humans, the vertebral column resembles a double “s” shape, which balances the torso above the hip (and creates the back problems we suffer later in life). At the top of the spinal column, the top vertebra, the atlas, has facets that balance the head and the second vertebra, the axis, has a prong that fits directly into a hole in the skull. This hole, which is called the foramen magnum, is at the back of the skull in higher apes, as in all quadrupedal animals. This allows the animal to keep its head up while it is trotting along the ground. In humans, the foramen magnum is at the base of the skull, allowing us to look forward as we walk. It also makes it hard to look forward when we crawl on all fours. Each of these modifications is diagnostic of humans and easily recognizable in the fossil record in specimens for which these anatomical areas are present.

Ardipithecus ramidus and the Origins of Bipedality

The origins of bipedality have traditionally been understood as having evolved at the end of the Miocene epoch, around 6 to 8 million years ago (Crompton, Sellers and Thorpe 2010) when the climate began to dry out and cool. Unfortunately, there are only scattered presumed hominin remains from this time period, all of which are taxonomically controversial and fragmentary and none of which have diagnostic postcranial remains. It has also been thought that the transition to bipedality likely did not happen all at once but in mosaic fashion (as evolution often proceeds) and this has recently supported by the fossil record. Up until a few years ago, the most widely-accepted model was that bipedality originated among a group of large-bodied hominoids that had adapted to the savannah-jungle fringe. The jungle, itself, was ceded to the precursors of the modern chimpanzees and gorillas and the savannah to the precursors of the modern baboons and other terrestrial monkeys. As a result, some workers (Crompton et al. 2010) suggested that both arboreal (tree-dwelling) and terrestrial locomotion might have been present in our earliest ancestors. Recent evidence has corroborated some parts of this model, but not others.

In 1994, the remains of a remarkable hominin, dated to 4.4 million years ago, were unearthed in the Afar Triangle of Northeastern Ethiopia. Examination of the surrounding deposits, however, yielded a conclusion that this hominin lived in a woodland environment, rather than a savannah/forest fringe environment (White et al. 2009a). Requiring over ten years of extrication from the surrounding rock and painstaking reconstruction, this fossil form, Ardipithecus ramidus (now represented by 110 individuals) yields diagnostic parts of the pelvis (Figure 4), as well as sections of the arms and skull (Figure 5) (White et al. 2009b). Although the base of the skull is not preserved, one striking aspect of humanity is present in the teeth. The canine (eye tooth) does not extend beyond the tooth row. Humans are the only hominins for which this is the case. In all other ape species, fossil and extant, the canine projects well beyond the tooth row.

Biomechanics specialist Owen Lovejoy and colleagues (Lovejoy et al. 2009) write about this species:

“The gluteal muscles had been repositioned so that Ar. Ramidus could walk without shifting its center of mass from side to side. This is made clear not only by the shape of its ilium, but by the appearance of a special growth site unique to hominids among all primates (the anterior inferior iliac spine). However, its lower pelvis was still almost entirely ape-like, presumably because it still had massive hindlimb muscles for active climbing.”

Figure 6 shows the intermediate nature of the pelvis of Ardipithecus ramidus compared to later hominins (Homo sapiens, Au. Afarensis) and chimpanzees (P. troglodytes).

Ardipithecus, then, represents a shift away from the primitive locomotion employed by the last common ancestor of our line and that of modern chimpanzees. Here is a hominin that maintained a link with its tree-dwelling past and yet had progressed toward the bipedal future. This evidence is striking because it firmly demonstrates that a species had arisen that was advanced in the human direction. Whether or not it led to the hominin forms that followed is not known but it clearly represents a phenomenal example of a transitional form in the human fossil record.

From this point on, the forms become noticeably more human in appearance, leading eventually our own species some four million years later. In his infinite wisdom, God had set us on a path toward our eventual communion with Him. That this path took such a long period of time and through so many varied forms of humanity is a testament to His creative power and patience.

#The Discovery of Australopithecus

The Taung Child

In the early 1920s, a young anatomist named Raymond Dart took a job at the University of Witwatersrand in Johannesburg, South Africa. Keenly interested in comparative primate anatomy, Dart had been advised to go to the Wit by the famed anatomist Sir Grafton Eliot Smith and, upon arrival, began work on the ancestry of South African primates.

North of Johannesburg lay the Buxton Limeworks where fossils were being blasted out by the thousands, and Dart, through a colleague at “the Wit,” informed the workers there that if they encountered anything interesting, he would be more than willing to receive it. One worker had been collecting fossils for several years and had two large crates of them. When these crates arrived in Dart’s laboratory, he examined them to see if they had any primate fossils. The first did not but the second revealed a beautiful specimen of a child’s partial skull and fossilized brain cast in it. Both were embedded in a limestone concretion, which took Dart 73 days to pry apart. Once he did, he discovered, based on the eruption pattern of the teeth, that he had the skull of a two to three year old child (see Figure 1 at left. He also noticed several odd things. While it was clearly a primate skull, the teeth, somehow, didn’t look right. As I mentioned in the last post, in all non-human primates, the canine (eye tooth) extends beyond the tooth row, even in infants. The canines of this skull did not. (See Figure 1 at left and for a detailed comparsion, see here and here.) He also noticed that, for a primate skull of two to three years of age, the brain was simply too large, being roughly twice the size of a comparable baboon skull. Further, he knew that this far south, there were no higher apes and, therefore, it was clearly not a chimpanzee skull.

The most important thing that caught his attention, however, was that, while not complete, the base of the skull revealed that the hole for the spinal column (foramen magnum, see the last post for explanation) was positioned at the bottom of the skull rather than at the back of the skull as in baboons. Dart could only conclude that, whatever this creature was, it walked upright and he took the unusual step of calling this new findAustralopithecus africanus or “Southern Ape Man from Africa.” It was the first confirmation of the prediction of Charles Darwin that the original ancestors of the human line would be found in Africa.

Dart met with considerable skepticism when he described his find in the journal Nature (Dart 1925). Not until the venerable palaeontologist Robert Broom backed his claims, did Dart’s phenomenal discovery begin to percolate through the field. Between 1924 and 1949, Broom and Dart made many discoveries of australopithecines in four other caves in South Africa. These solidified the hypothesis that these finds were not aberrant apes or deformed fossils, as some thought, but were, in fact, in a line that diverged from apes and led, eventually, to humans.

The Definition of a Species in Living Populations

Before examining the appearance and proliferation of the australopithecines, which began around 4.0 million years ago, a short assessment of the nature of palaeospecies is necessary. As the marriage of evolutionary biology and mathematics grew to yield the fruitful field of population genetics, a problem still remained: how to scientifically define a species. Even when working with known populations, the problem of where to draw the line between two groups remained.

In 1942, evolutionary biologist Ernst Mayr, working with bird collections in the American Museum of Natural History, developed the “Biological Species Concept” which was as follows: “species are groups of interbreeding natural populations that are reproductively isolated from other such groups.” (Mayr 1942) This definition revolutionized the study of biological species and populations by providing a mechanism for the formation of species and showing the importance of natural selection and its effect on the individual organism. This quickly became the de facto definition of species and helped to usher in the “new synthesis” of evolutionary biology in the 1940s and 1950s, a definition that could work for researchers no matter what they were studying…as long as it wasn’t fossils.

The Definition of a Species in Extinct Populations

Because fossils give us no information about breeding practices, population size or morphological diversity, they add yet another dimension to the species problem. The ultimate question a palaeontologist faces when holding two fossils is, “how different are these two individuals and could they conceivably have been part of the same breeding population?”

There are typically two different concepts of species definitions as they apply to the fossil record: the phenetic concept, which uses all of the observable characteristics a fossil has and relates them to other like fossils, and the phylogenetic concept, which focuses on traits one fossil has that are different from like fossils around it. As Wood and Longeran (Wood and Lonergan 2008) note:

In practice most researchers involved in hominin taxonomy use one or other version of the PySC [phylogenetic species concept]. They search for the smallest cluster of individual organisms that is ‘diagnosable’ on the basis of the preserved morphology. Because in the hominin fossil record most preserved morphology is craniodental [head and teeth], diagnoses of early hominin taxa inevitably focus on craniodental morphology.

Remember that a phylogeny is the evolutionary history of a species. In most cases, this is very hard to discern. As a result, the adaptive radiation of the australopithecines, in some ways, is a classic example of collateral ancestry that we discussed earlier (see this post) in the sense that, while we may not know who was related to whom, all of these species show transitional characteristics. As a result, most palaeontologists have treated the radiation of australopithecines as reflecting many different species. Whichever species concept one uses, the radiation, as evinced from the fossil record, was extensive, beginning around 4.0 million years ago and lasting to possibly as late as 1.2 million years ago (see Figure 2 below, adapted from Science Magazine).

The discovery by Dart of Australopithecus africanus served as a springboard for later excavators and its characteristics a template from which to compare other finds. Since Dart’s fateful discovery 97 years ago, ten more species of Australopithecus have been discovered, ranging from very gracile and petite forms to very large and robust forms. Figure 2 shows the current presumed australopithecine taxonomy. The red bars show the inferred time span of each species. Missing is the newly discovered Australopithecus sediba, whose placement is not currently known but is thought by the discoverers (Berger et al. 2010) to be descended from A. africanus. In the next post, I will address the radiation of the earliest australopithecines, including the famous “Lucy.”

For reference, Figure 3 below shows the Australopithicus specimens in time-perspective to other hominid species that have discovered so far.

Figure 3 Australopithecus in Perspective (from Science Magazine)

Australopithecus Conquers the Landscape

Australopithecus anamensis

I described the discovery of the first Australopithecus in South Africa by Raymond Dart. Beginning with the work of Dart and venerable palaeontologist, Robert Broom, an extensive range of discoveries has been made that continues to the present day.

The earliest known species from the genus that Dart discovered is known asAustralopithecus anamensis. Its remains are, sadly, still quite fragmentary. Working at the sites of Kanapoi and Allia Bay in Lake Turkana, in Kenya, Richard Leakey and others unearthed the partial remains of a number of individuals, which are securely dated to between 4.0 and 4.2 million years ago. By comparison, Ardipithecus ramidus (see Figure 1) is dated to around 4.4 million years. More recently 30 specimens of Australopithicus anamensis from at least 8 individuals have been found in Ethiopia and they have been dated at a similar age (see here for an analysis of the rock strata and age of the formations in which the specimens were found.)

Currently, the remains attributed to Australopithicus anamensis consist of several jawbones, some lower faces, more than 50 isolated teeth, skull fragments, several sections of lower arm and a section of a tibia, just below the knee (See Figures 2 and 3). Nonetheless, it is possible, for reasons discussed below, to determine a great deal about how this species moved around, the kinds of things that it ate and, critically, how it differed from its predecessor, Ardipithecus, and the forms that would come after it.

It has been determined that this species inhabited sparse woodland, river bank environments and open grassland, a greater range than that in which Ardipithecuslived. This is based on the similarities between the deposits from Kanapoi, Allia Bay and those of Australopithecus afarensis, the hominin that follows Australopithecus anamensis, temporally. In addition there has been an extensive analysis of accompanying fossil species found at the Ethopian site where specimens from eight A. anamensis individuals have been found.

In addition to the increase in range, certain elements of the skeleton are present that show a clear trend toward the forms that would come later. These include significant changes in how the teeth and palate are arranged, the shape of the teeth (Figure 2), and the morphology of the tibia (Figure 3).

Figure 2 (above, left). Lower Jaw bone of two specimens of Australopithecus anamensis. Figure 3 (below, right). Different views of the same tibia bone from Australopithecus anamensis.

In Ardipithecus, the dentition was very similar to that of modern chimpanzees, with the exception of the size of the canine, which was shortened. The teeth were geared toward a fruit and leaf diet, with occasional meat thrown in, such as you would find in a forest environment.

In Australopithecus anamensis, however, the teeth had much thicker enamel, they were larger and had flatter grinding surfaces that would have been more suited to nuts and other hard foods. This suggests that this hominin would have been well-adapted for life in open grassland and savannah.

The orientation of the tibial shaft indicates that it was positioned directly up and down in relation to the foot and the femur, suggesting that the individual walked completely upright. The length of the radius fragment and its comparison to the tibial fragment further attests that this individual had arms that were elongated, like Ardipithecus. It seems likely, therefore, that like ArdipithecusA.anamensisspent quite a bit of time off the ground.

It is tempting to speculate about the cognitive abilities of Australopithecus anamensis relative to Ardipithecus ramidus. We have no evidence that Ardipithecus existed outside the forest environment. Based on the taphonomic evidence, we strongly suspect that A. anamensis existed in the fringe and savannah. We do know that the vast majority of modern primates have home ranges that are restricted to one kind of biome. For example, Orang-utans only live in the forests of Borneo and Sumatra while Spider and Howler monkeys only exploit the forest canopies of Central America. While these examples certainly reflect a stable evolutionary response to particular environments, their inability to move beyond these environments and the need for conservation efforts to preserve them reflect a level of cognitive ability that appears to be restricted. If A. anamensis could survive in both the forest/fringe and savanna environments, it suggests an increase in cognitive abilities for this species. More evidence will be necessary to lend credence to this hypothesis.

Australopithecus afarensis

In 1973, working with a local team of fossil hunters, Maurice Taieb went to an arid stretch of land in the Afar Triangle of Ethiopia to an area called Hadar. A year later, Don Johanson, a member of his team discovered one of the most famous of all fossil hominin discoveries ever made. Exploring 3.4 and 3.6 million years old deposits, he discovered the fragmentary remains that constituted 40% of the skeleton of a small adult female (Figure 4) . This individual was nicknamed “Lucy” after the Beatles’ song “Lucy in the Sky with Diamonds” which played in the camp during the analysis of the remains. The team named the species she represented Australopithecus afarensis, because she had been found in the Afar triangle. Johanson, together with M. Edey, went on to pen the New York Times BestsellerLucy: The Beginnings of Humankind. This book catapulted Lucy onto the national stage and fueled research into the biological origins of humankind (Johnanson and Edey 1980).

When Lucy was examined, it was found that the shape and position of the the teeth and jaw as well as the hip and long bone fragments put her almost perfectly intermediate be tween the ape position and the human position. Although she had the overall size and rib cage structure of a chimpanzee, her pelvis and leg bones were perfectly adapted for bipedalism. It was in the teeth and palate that the clearest transitional characteristics existed (Figure 5, right). In modern humans (5c), the dental arcade (tooth row) is in the shape of a parabola, like the Gateway Arch in Saint Louis. In apes (5a), it is a sharp “U” shape. In A. afarensis (5b), it is intermediate, tending toward the ape condition.

In apes, there is a space (diastema) between the canine and the second incisor (bicuspid, if you prefer) to allow room for the long lower canine when the ape closes its mouth. In A. afarensis, the canine is human-sized and the diastema, while still present, is smaller. In apes, the first premolar is rotated relative to the tooth row and has a very high cusp so that it creates a sharpening surface for the opposite canine when the two teeth come together. In Lucy, the cusp is somewhat lower and the premolar is only slightly rotated. In humans, the cusp does not extend above the tooth row and there is no rotation at all.

The case for habitual bipedalism received added support from a site much further south than where Lucy had been found. In 1976, Andrew Hill, a digger in Mary Leakey’s team, working at the site of Laetoli, in Tanzania, unearthed a set of hominin tracks that had been covered by a now extinct volcano. These footprints, which extend approximately 80 feet across the plain, have been securely dated at 3.6 million years and show where two individuals walked side-by-side (Figure 6). The tracks are significant in that they demonstrate that the individuals who made them had arches and practiced the characteristic “toe-off” pattern of gait practiced only by hominins. The presence of A. afarensis skeletal remains nearby at the same level provided the link to the footprints.

By the time A. afarensisappears in the lineage all clear evidence of spending time in the trees was gone. On the foot, the arch had become prominent and the big toe, which had been slightly off-set in Ardipithecus and possibly Australopithecus anamensis, was firmly in-line with the other toes. The presence of the arch allowed for easy toe-off locomotion and would have been disadvantageous in climbing trees because it contributes to the rigidity of the foot. This was a species that was not just optimized for bipedality, it had become its only form of locomotion Furthermore, as noted, taphonomic evidence indicates that this species could exist in the forest and fringe environments. Its presence in both the Afar triangle and near Lake Turkana (nee Lake Rudolf) further suggests that it had a range of several thousand miles (Figure 7, right).

Kimbel and others have suggested that the similarities in traits between A. anamensis and A. afarensis represent an ancestor-descendant relationship, with A. afarensis representing the more advanced stage in hominin evolution(Kimbel et al. 2006).

Stone Tools: A Cognitive Shift

With Australopithecus afarensis came another striking evolutionary development. While A. anamensis and A. afarensishave been shown to have adapted to the forest/fringe and savannah environments, it is with A. afarensis that we have the first evidence of behavior that is directly cognitive in nature: the use of stone tools. At the site of Dikika, in Ethiopia, very near the site of recovery of an almost complete A. afarensis skeleton, animal bones were discovered dated to at least 3.39 million years ago that demonstrate distinctive signs of human action: cut marks. As McPherron et al. write:

The cut marks demonstrate hominin use of sharp-edged stone to remove flesh from the femur and rib. The location and density of the marks on the femur indicate that flesh was rather widely spread on the surface, although it is possible that there could have been isolated patches of flesh. The percussion marks on the femur demonstrate hominin use of a blunt stone to strike the bone, probably to gain access to the marrow. (McPherron et al. 2010) (For video summary of discovery, see here)

These authors are quick to point out that there is no way to determine whether or not these marks were made by tools that were modified for this purpose or made with the first available sharp rock, although the authors note that rocks found in association with the bones had been transported over six kilometers from their original location. This reflects advanced behavior by these hominins, though, including the first consumption of meat known in the fossil record.

Figure 8. Cut Marks on 3.35 Million year old Bovid Femur (from Nature)

With Australopithecus afarensis, however, a new hominin was on the landscape—a hominin that could adapt to new environments and, to a limited degree, adjust the environment around them to meet their needs. Without the adaptations necessary to remain in the trees for any length of time, and with the ability to balance and walk in a truly human fashion, the fact that they no longer needed to use the hands for support or grasping, freed them up for other uses. As A. afarensis moved about the landscape, these uses became evident: they modified what they had at their disposal.

It is unfortunate that we do not know whether these hominins created the tools to make these marks or used what was available to them. If they brought stones with them to butcher animals, though, it means that they were the first hominins that did more than react to their environment; they modified it to their uses.

The Dispersal of the Australopithecines

As we’ve seen, until approximately three million years ago, australopithecines were restricted in variation to Australopithecus afarensis, the successor to Australopithecus anamensis. This hominin has been found in the north at Hadar, Ethiopia, and as far south as Tanzania. Subsequent to this time period, however, the australopithecines as a genus underwent a dramatic expansion and, eventually, would be found in all of eastern and possibly central Africa.

The Lack of Acceptance of Australopithecus and the Piltdown Forgery

Raymond Dart, discoverer of the first australopithecine, the Taung child skull, met with lukewarm to tepid response when he described his find in the journal Nature. One of the reasons for this is that, to the early 20th century eye, it looked very ape-like, and it was hard for many to grasp that there was any connection between it and the forms that followed. The other reason is that the path to humanity was thought to already exist elsewhere in the form of Eoanthropus dawsoni, the fossil remains from the Piltdown Commons, in England.

The Piltdown forgery ranks as one of the best scientific hoaxes of all time. Charles Dawson unearthed purported hominin fossil remains from a gravel pit at Piltdown Commons, East Sussex County, in 1912 that consisted of a mostly complete skull and partial jaw in association with extinct mastodon and hippopotamus fossils (See Figure 1). This was published in the Quarterly Journal of the Geological Society (Dawson and Woodward 1913) and became the crown of English anthropology, eliciting the support of most of the top anthropologists and anatomists of the day, including Sir Arthur Keith, Sir Arthur Smith-Woodward, Grafton Eliot Smith and William King Gregory.

The find, which was dated biostratigraphically to the Middle-Pleistocene, showed that evolution of the braincase preceded evolution of the rest of the head and jaw. Consequently, when Dart’s australopithecine find was described with its human-sized teeth and small braincase, it didn’t fit the pattern established by Piltdown and was, thus, denigrated by the researchers in the field. However, as more human remains were found in the 1930s and 1940s that resembled Dart’s find, Piltdown’s uniqueness became peculiar. Further, nothing else emerged from England itself that resembled Piltdown. As researchers around the globe began to assemble their human origins charts and timelines, Piltdown became increasingly hard to accommodate within any evolutionary framework.

In the early 1950s, Kenneth Oakley and Josef Weiner secured the rights to examine the remains using a new relative dating method that had been recently been calibrated, fluorine analysis. The basis behind this technique is simple: as organic material sits in the ground, it soaks up fluorine. The longer it is there, the more fluorine it soaks up. In this way, some fossils could be said to be older than others and rough comparisons could be made. Oakley’s analysis initially suggested that the find was much more recent than originally thought (Oakley and Hoskins 1950) This sowed the first seeds of doubt about the find. Eventually, a more detailed analysis was undertaken by Weiner, Oakley and Wilford Le Gros Clark, resulting in the publication “The Solution of the Piltdown Problem” (Weiner, Oakley and Le Gros Clark 1953). They discovered that the teeth had been filed down to make them look old, the jaw and isolated teeth were not the same age as the cranium but were, rather, modern in age, and that the remains had been stained to give them an old appearance. These findings led to a public outcry and the whole house of cards came down. Subsequent analyses revealed that the jaw was, in fact, that of an orangutan, the mastodon and hippo remains had metal knife marks, and the fossil mastodon remains were from Tunisia.

To this day, the identity of the Piltdown forger remains unknown. The weight of suspicion has fallen, in recent years, on the original discoverer, Charles Dawson, who likely had the means to carry out the prank. Sadly, Dawson contracted septicemia and passed away in 1916, possibly carrying this information with him to his grave. One of the best accounts of this forgery is by John Walsh, called Unraveling Piltdown (Walsh 1996). Perhaps one of the most important lessons from the Piltdown experience is that it demonstrates a classic example of the self-corrective capacity of science. Once the weight of Piltdown had been removed from the field, the australopithecine discoveries in Africa began to make sense in the context of the larger picture of human origins.

Australopithecine Phylogenetics

Australopithecine systematics is, like that of the earliest birds, a confused business, with many different competing hypotheses about where each species fits in the grand scheme of things (See Figure 2 below). To top this off, it is not clear from which of these lines Homo emerged.

Based on the best current weight of evidence, it is now commonly thought that between two and three lineages of australopithecines emerged from the line that came from A. afarensis. It is not possible to infer direct ancestor-descendent relationships between these forms. All that we can surmise at the moment is that at around 3.0 million years ago, A. afarensis was the only hominin on the landscape and at 2.5 million years ago, there were multiple forms, spanning the geographical distance between Ethiopia and South Africa with likely remains in Chad.

The East African Forms

Australopithecine species tend to be found in two general forms: a gracile, or smaller and lightly built, form and a robust, or larger and more heavily built, form. While some have argued that the robust australopithecines belong in a separate genus, Paranthropus (Grine 2007), this is a minority position within the field. For our purposes, they will be subsumed within the genus Australopithecus.

At around 2.5 million years ago, a new form was found in Ethiopia that appeared to be a scaled up version of A. afarensis. Called Australopithecus aethiopicus, this species had a long, low cranium with flared cheekbones and attachment areas for very powerful chewing muscles on its face (See Figure 3). To go with this, A. aethiopicus also had, on the top of its head, a large sagittal crest. Work with modern-day gorillas, which also have this feature, has shown that this is not a genetic trait but appears as a result of bone deposition on the top of the head through continuous grinding of nut and plant substances. Unlike the gorilla version, however, which is focused directly on the top of the cranium (vertex), the A. aethiopicus manifestation is toward the back of the cranium. This form had an average cranial capacity of around 410 cubic centimeters. For comparison purposes, the average modern human cranium is approximately 1450 cubic centimeters in capacity while chimpanzees average 375 cubic centimeters.

Also from this time period is a form similar to A. afarensis in brain size and gracility, Australopithecus garhi (“surprise” in the Afar language). The teeth are slightly larger than those of afarensis (See Figure 4). In overall body shape, however A. garhi was far more modern, with the ratio of upper arm length to upper leg length much closer to those of later hominins (Asfaw et al. 1999).

Slightly later in time, from around 2.2 million years ago, came Australopithecus boisei. This form was originally found in 1959 by Mary Leakey, in the Olduvai Gorge area near the Serengeti Plains, in Tanzania, where she and her husband, Louis, had been digging since 1951. This is known as a hyper-robust australopithecine. Comparisons with A. aethiopicus strongly suggest that the facial architecture of A. boisei is very similar, yet larger in size. This has led researchers to surmise that there is an ancestor/descendent link between the two species. A. boisei has a slightly larger cranial capacity of 510 cubic centimeters but otherwise retains all of the characteristics of A. aethiopicus, including the sagittal crest, the scooped-out facial appearance and wide, flaring cheek bones (see Figure 5). It has been hypothesized that these forms subsisted primarily on a vegetative diet consisting of hard nuts, roots and berries because the rear teeth were much larger than the front ones and considerably larger than those ofA. afarensis. This eventually led to the nickname “nutcracker man.” This hypothesis has recently been challenged, however, by research that suggests that the primary diet of this hominin was grasses (Cerling et al. 2011). A. Boiseiis found down to approximately 1.2 million years ago.

The Dispersal of the Australopithecines

The South African Forms

As noted in the last post, the discovery of the Taung child in South Africa fueled interest that other hominins could be found as well. With the help of noted anatomist Robert Broom, and anthropologist John T. Robinson, Raymond Dart excavated several other sites in the South African cave system, Makapansgat, Swartkrans, Sterkfontein and Kromdraai, all of which yielded australopithecine remains of both an early gracile form and later robust form. The earlier form, dated to between 3.0 and 2.0 million years ago and to which the Taung find belonged, was calledAustralopithecus africanus (see Figure 6). Exact dating for these cave sites is hampered by the fact that the cave openings are vertical and it is not clear how the hominins got there. Unlike the east African forms, A. africanus was a very lightly built form, with no crests of any kind. The overall cranial capacity of the finds is between 430 and 520 cubic centimeters, slightly larger than that of A. afarensis and comparable to the east African forms. Like the east African forms, the teeth of this form were larger in the back and smaller in the front than A. afarensis suggesting to some an herbivorous diet.

Slightly more recent in time is A. robustus. This is a scaled-up version of A. africanus and continues the trends seen in that form (See Figure 7). Although having a generally similar facial structure as A. africanusA. robustus also has crests like the eastern African forms, suggesting a similar dietary adaptation. There is also a continuation of the trend toward larger back teeth and smaller front teeth to accommodate this. While A. robustus and A. boisei are both considered “robust” australopithecines, the considerable differences in their facial architectures suggest to most researchers different evolutionary trajectories.

A recent discovery has been made by Lee Berger and colleagues (Berger et al. 2010) at the site of Malapa in South Africa, of yet another form of Australopithecus, which cannot be accommodated into the sequence of A. africanus and A. robustus, and is different enough from each of them to warrant its own species designation: A. sediba. This form is characterized by having a small cranium with no crests and a flat face, in contrast with all other known australopithecines (See Figure 8). Berger suggests that this form is descended from A. africanus and existed parallel to A. robustus. It has also been suggested that there are post-cranial elements in the hip and leg bones that align it with later Homo, although, at this point, the evidence for this position is scant.

The Odd Men Out: Kenyanthropus Platyops and Australopithecus Bahrelghazali

Up until the last few years, australopithecine evolution had been assumed to have taken place in the entire east African Rift Valley and South Africa. That changed in 1995 when researchers working on the banks of the Sahel River in Chad, discovered what they described as yet another australopithecine, A. bahrelghazali. Nicknamed “Abel”, this find was initially dated to between 3.0 and 3.5 million years ago, and consists only of a jaw fragment with six teeth. Since its discovery, the date of the find has been challenged by Beauvilain (Beauvilain 2008), who argues “Abel was collected at the foot of the shoreline of the last episode of Lake Megachad, which is only a few thousand years old.” While this does not imply that the find is this old, it does cast doubt on the ability to determine just how old it is. The morphology does appear to be australopithecine, however, extending the possible reach of this remarkable genus out to central Africa. Little has been said about it since then, however.

The other find of note was a discovery in northern Kenya, in Lomekwi of a mostly complete but crushed cranium and some facial bones of an individual that shows considerable facial flatness and is lacking in any of the specializations present in the robust australopithecines in terms of dietary adaptations (See Figure 9). It was hence called Kenyanthropus platyops (flat-faced man from Kenya). Dated to approximately 3.5 million years ago, little is known about this find. Its cranial capacity is between that of A. afarensis and A. africanus, at around 400 cubic centimeters (Leakey, et al. 2001). Due to the condition of the cranium, it is difficult to draw any inferences about where this find fits in the phylogeny of the early hominins, and some authors are relegating it to a regional variant of A. afarensis (White 2003). Michael Balter, in fact, recently asked the question Whatever happened to Kenyanthropus platyops?, and the fossil seems to have not generated much interest in recent years.

The Place of Australopithecus

It is tempting to look at these remains and think privately, “these are nothing but apes. What is the fuss?” Such has been the viewpoint of the Institute for Creation Research’s Duane Gish (Gish and Research 1985) and John Morris, who remarked “From the neck down, certain clues suggested to Johanson that Lucy walked a little more erect than today’s chimps. This conclusion, based on his interpretation of the partial hip bone and a knee bone, has been hotly contested by many paleoanthropologists” (Morris 1994). This is incorrect. There was never any doubt in any of the researcher’s minds that from A. afarensis, the australopithecines walked upright, albeit with a gait not quite like that of modern humans. It is, further, instructive to compare the skulls of australopithecines and chimpanzees side by side (Figure 10). This shows several of the characteristics in the australopithecines that are derived relative to the ape condition. First, the brain case is decidedly larger, on the order of 100 cubic centimeters, and, second, the teeth do not extend beyond the tooth row as they do in the chimpanzee. While this comparison is certainly artificial in that the chimpanzee is a modern animal, the fact remains that the brains of australopithecines were already advanced beyond any known ape species either then or now. As importantly, however, is that the foramen magnum hole is always at the bottom of the skull in all australopithecine remains for which that area of the skull is present, indicating bipedality (movement on two rear legs), a condition never found in apes.

The Oldowan Tool Tradition

At the site of Gona, in Ethiopia, stone tools were unearthed dating to between 2.4 and 2.6 million years ago. More advanced than those used by A. afarensis, these consisted of crude choppers, bifaces and rudimentary blades. Other tools have been found at Olduvai (the type site) but none in direct association with any hominin remains. While it is thought that the users of these tools may have been australopithecines, there is simply no direct evidence to support this.

The Extinction of the Australopithecines

In both east and south Africa, the australopithecines hold sway until approximately 1.2 to 1.1 million years ago. Then they simply disappear. Remains are few enough that it is not possible to say for sure why or over what period of time this happened. As can be surmised from the evidence of the dentition and facial muscles, the australopithecines became very dietarily specialized, leading them down a restricted evolutionary path. Consequently, the most widely supported explanation for their extinction is that they were simply out-competed by the new kid on the block: Homo, which first makes its appearance around 2.3 million years ago. With the advent of Homo came a hominin with a vastly expanded braincase and direct association with stone tools.

We have now covered the ground between the earliest demonstrable hominins, in Ardipithecus and the most prolific ones, the australopithecines. Next, we will move to forms that begin to show the characteristics that we can recognize, from a physical perspective, as human.

#The Rise of Early Homo

Our Journey Thus Far

Thus far, we have journeyed from the forests of the late Miocene/Early Pliocene at 4 and half million years ago to the open savannah at a little over one million years ago. We have seen perhaps our first forebears, Ardipithecus ramidus in Northeast Africa, walk upright, albeit awkwardly at first—the first primate to do so. Although not human as we would know it, this step was the first of many and, coupled with a smile that contained human-sized teeth, it signaled the arrival of a different kind of primate. The form that followed, Australopithecus, showed even more changes. With the use of true bipedalism and the first evidence of tool use, this form underwent rapid adaptive radiation across the Northeast, central east and South African landscape, eventually reaching an estimated nine different species, some small and slight, others larger and more robust. From approximately 4 million years down to 2 million years ago, the australopithecines were unchallenged on the savannah. It was at this time that another form appeared on the landscape—early Homo.

With the transition from Australopithecus to early Homo came changes as great as those that had come before. In early Homo came a hominin with a larger, rounder cranium and evidence of clear stone tool production.

From Whence Came These Beings?

Unfortunately, the path from Australopithecus to early Homo is shrouded in mystery, with no clear hominin form considered decisively to be the progenitor. One reason for this mystery is that the first specimens of our line are extremely varied in morphology—so much so that there is considerable disagreement about how many species are present (Kramer, Donnelly, Kidder, Ousley, & Olah, 1995). Although there is much material comprising early Homo, many of the finds are incomplete, consisting of partial crania, jaws, sets of teeth or long bone fragments. In the early stages, there was little emphasis on constructing species names for the early Homo fossils that were coming out of the ground from the 1960s on (Richard E. Leakey, 2009). It was easier to just call them Homo. As I will show in detail below, the differences in size and shape of these early Homo forms has led researchers to divide them into three separate species, Homo habilis, the smallest and most primitive form, Homo rudolfensis, the primitive but larger form, and Homo ergaster, the largest of the three. While both H. habilis and H. rudolfensis had faces that tended to be similar to late australopithecines, these traits were gone by H. ergaster, which exhibited a much flatter, more modern face and much larger cranium.

All three species, Homo habilis, Homo rudolfensis and Homo ergaster, (Figure 1) appear in the fossil record between 2.3 to 1.8 million years ago (Prat et al., 2005). They, therefore, overlap with the late, robust australopithecines, which were very specialized towards diets of grass, nuts and berries.

One possible path is from Au. afarensis to HomoAu. afarensis is very generalized for an australopith and does not show the specializations of the later robust forms in the large rear teeth, massive chewing complex or wide, flaring faces. There is, however, considerable time in between this form and the appearance of early Homo—on the order of one and a half million years. It has been suggested that Au. afarensis gave rise to both Au. aethiopicus which shows some of the same characteristics: the crest on the top of the head and very scooped face, and Au. africanus, which is also a small form. Supporters of this argument then posit that Au. africanus gave rise to earlyHomo.

Others argue that Au. africanus is too specialized to have given rise to any of the early Homo forms. Au. africanuspossesses very strong facial features such as the large anterior pillars that show up in modified form in the south African Au. robustus but not in Homo. This is a vertical ridge of bone that extends up from the canine to the outside edge of the nasal cavity and is distinctive for these hominins. The other problem is that the earliest Homo shows up in East Africa and Au. africanus is only found in South Africa.

Berger (Berger et al., 2010) argues that Au. sediba possesses traits aligning it with Homo and that it may have given rise to one of the later forms. Its late date of 1.8-1.,9 million years excludes it from being the progenitor of eitherHomo habilis or Homo rudolfensis, however.

It has even been suggested that early Homo derives from Kenyanthropus platyops, which if you will remember from the last post, is a fossil find that dates to 3.5 million years ago and that appears to have a very flat face in comparison to the early australopithecines which is argued to be a more modern trait. (Cela-Conde & Ayala, 2003). This position is not well supported because the find was so badly crushed post-mortem and is so badly distorted that very little can be said about it taxonomically and it has been described by other researchers as anAustralopithecus afarensis variant.

East Africa

Homo habilis

In 1961, Louis Leakey’s team discovered the parts of a skull, and some hand and foot bones at Olduvai Gorge. Two years earlier, workers had found the spectacular robust Australopithecus boisei skull, OH5, at this same location. These remains, he concluded were different from the known samples of Australopithecus. The brain size of this individual, OH 7, was 630 cubic centimeters (cc), fully a hundred ccs larger than the just discovered, Au. boisei specimen (L. Leakey, 1961). Not only that but in comparison to the australopithecines, the crania were more lightly built, rounder and slightly larger. The back teeth, which were very large in the robust australopithecines, were smaller and more closely approximated our own dentition. The face was, overall, slightly flatter although it still had the “scooped” appearance of the gracile australopithecines (see sidebar). One such skull was OH 24 (short for Olduvai Hominin 24) (Figure 2), which demonstrates the evolved morphology. This cranium was estimated to have a cranial capacity of slightly less than 600 cc, still far larger than any australopithecine species.

Leakey was so convinced that these represented a new, advanced species that he called it Homo (For an excellent review of the earliest finds, see (Schrenk, Kullmer, & Bromage, 2007). As more remains were discovered at Olduvai Gorge, in 1964, Homo habilis (handy man) was formally named. (L. S. B. Leakey, Tobias, & Napier, 1964). This was the first time that such a designation had been given to remains that were so manifestly primitive compared to modern humans and it was very controversial. For example, the cranial capacity was fully 900 cc less than the 1500 cc capacity of modern humans. Even now, fifty years later, controversy still swirls around this species, with some authors arguing that it belongs in the genus Australopithecus. Its primitive face and other skeletal features (for example the finger bones are curved as in Au. Aafricanus.) suggest that it is more like members of the australopithecines than it is like Homo.

Homo rudolfensis

In the late 1960s, Richard Leakey joined his father in the hominin adventure. Richard had come into palaeoanthropology somewhat reluctantly having rejected his father’s encouragement to follow in his footsteps. Instead, he had made a name for himself as a big game safari leader. As Don Johanson writes:

He proved to be extremely good at this. As a result, by the time he was in his early twenties he had learned a great deal about how to get about in rough country. It was that experience, and obvious talent for organization, which persuaded Louis that Richard should handle the Kenya end of the expedition, even though he had no training in anthropology or geology whatsoever. He knew quite a lot—how could he not, growing up with Louis and Mary Leakey as parents?—but his formal education had stopped in high school (Johanson & Edey, 1981)

Biostratigraphy means of applying relative chronological dates to geological formations based on the kinds of fossils that are present in them.

After a few years working at Omo, in the early 1970s he took an expedition team to the Koobi Fora region of Lake Rudolf (now Lake Turkana, See Figure 3, a map of site locations in East Africa) and, in 1972, unearthed one of the most famous of all hominin fossils, the KNM-ER 1470 skull (Figure 4) (Day, Leakey, Walker, & Wood, 1975; R.E. Leakey, 1973). Although he initially dated the find to around 2.9 million years old by palaeomagnetism, discrepancies arose in the form of faunal correlations. The pigs that were found in the same level as ER 1470 were securely dated to around 1.8-1.9 million years at other sites. The level was subsequently re-dated by Potassium-Argon and found to be 1.9 million years old, making it coeval with the robust australopithecines of the region (Johanson & Edey, 1981). This has become the settled date of this fossil, relying not just on biostratigraphy (see sidebar) but radiometric dating.

The initial problem this skull created was that it presented very different morphology from any of the Olduvai specimens, having a much larger supraorbital region and larger, inflated cheeks. Originally subsumed within Homo habilis, the discoverers felt that the difference in size between the Olduvai hominins and the larger fossils from Koobi Fora could not be accommodated within one species. The new specimen had a rounder cranium, flatter face and cranial capacity between 700 and 750 cc., a full half again as much as the largest australopithecines and between 50 and 100 cc greater than the Olduvai Homo habilis sample.

It has been suggested by Walker and others (Strait, Grine, & Moniz, 1997; Walker, 1976) that the rush to call these remains Homo belies their generally australopithecine-looking faces, introducing an unnecessarily large amount of variation into the genus. They suggest that these forms should be called large-brained australopiths. However, cladistic analyses carried out by several workers involving both quantitative (skull measurements such as skull length, width and facial height) and qualitative traits (whether or not a particular trait was present) demonstrate that early Homo forms represent a group that is highly distinctive compared to all australopithecine species (Strait & Grine, 2004; Bernard A. Wood, 2009).

In addition to the large Homo crania found at East Rudolf, a smaller form was found that was similar in size to the Olduvai Homo sample with the same characteristics as the larger East Rudolf sample. One, in particular, KNM-ER 1813 (Figure 5), had a cranial capacity similar to that of the largest australopithecines, around 510 cc. It has been suggested alternately that the large size differences between the larger and smaller forms at this site represent sexual dimorphism (the difference in size between males and females of the same species) (Rightmire, 1993) or that they represent the presence of H. rudolfensis and H. habilis at the same location (Schrenk, et al., 2007).

The Oldowan Tool Tradition

Taxonomy is the science of classifying and ordering relationships based on a characteristic or set of characteristics.

As controversial as the taxonomy (see sidebar for definition) of early Homo is, there remains another vexing problem: who was the creator of the Oldowan tools that are found at many sites, dating to between 2.6 and 1.7 million years (Figure 6) As Roche et al. (Roche, Blumenschine, & Shea, 2009) note, based simply on chronostratigraphic context, these tools are found in indirect association with Australopithecus boiseiAustralopithecus garhi, and all three species of early Homo. They consist of edge and end scrapers and are, by modern standards, crudely made. Arguments have been put forth by several different workers in support of both australopithecine and Homo manufacture. The argument for australopithecine manufacture is based on several assertions: The earliest evidence of stone tools is at the site of Gona, in East Africa at 2.3 million years ago (Prat et al., 2005) and the most prevalent hominin around at the time was Au. boisei. Additionally, stone tools are found in the same chronological level as Au. boisei (especially at Olduvai). Finally, Susman has argued that Au. boisei possessed a precision grip necessary for tool manufacture (Susman, 1991).

The argument that early Homo made the tools, on the other hand, rests not just on stratigraphic associations but also on the premise that increased brain size would confer greater cognitive thought, and, coupled with reduction in back teeth may reflect greater reliance on meat, the procurement of which would require tools like those found in the Oldowan assemblages.

All we know at the moment is that the stone tools were present and that they were made by a hominin species that had the cognitive thought level to construct them.

Evolution in Early Homo

Earlier, I detailed the arrival of early Homo on the landscape and the differences of these forms from contemporary australopithecine species. The australopithecines, while possessing bipedal locomotion and, perhaps, rudimentary tool use, were characterized by having small brains, largely ape-like faces, reduced stature and primitive characteristics reminiscent of their ape ancestry. The advancements of their successors, manifested in slightly increased cranial size, more flattened faces and demonstrated stone tool use were sufficient to cause most anthropologists to differentiate these hominins from the australopithecines, assigning them to the genus Homo.

There was, however, some controversy surrounding this decision and not all agreed (Strait, Grine, & Moniz, 1997; Walker, 1976). The general consensus, however, was that there were two species, Homo habilis and Homo rudolfensis present on the landscape between 2.2 and 1.8 million years ago (the above graph lists a third Homo species, ergaster, which we will discuss in greater detail later in this post).

South Africa

So far, we have focused on early Homoremains in eastern Africa. Now we can turn our attention to the rest of the continent. In 1953, J.T. Robinson discovered skull fragments in an overhang at Swartkrans cave in South Africa, (the site of many australopithecine discoveries) that, when assembled (SK 847, Figure 2) some years later, demonstrated earlyHomo affinities. This find established the range of early Homo to at least 2500 miles, from East Africa down to the southern end of the continent. (Curnoe, 2010). It is thought that this cranium dates to between 1.8 and 1.5 million years ago but the fossil was not found on a habitation floor, the age remains uncertain.

In the 1970s, more work at the nearby cave site of Sterkfontein yielded a partial cranium that was also included within the genus Homo, although a firm designation was not given. It is now thought to be Homo habilis. This skull was found above a layer with Au. africanus remains, although it is not clear what relationship the two hominins may have had. Associated with the find were numerous Oldowan tools. This fossil was found on the surface of the cave and, based on associated fauna, it has been given a date range of between 2.0 and 1.5 million years ago. Sadly, at this time, these are the only specimens that can be attributed to earlyHomo in South Africa. This may reflect a limited migration of these forms to this area.

At least one investigator, Darren Curnoe, has examined the South African material and has argued that morphological differences exist between these finds and those from east Africa. In light of these differences, he has proposed a separate species, Homo gautengensis. This is based on the appearance of characteristics such as a mid-line keel (a ridge on the top of the head), a generally wider jaw, larger molars than those found in other early Homo remains, and a more rounded cranium. At present, however, this argument has received little support. Most researchers are content to label these forms Homo habilis.

Homo ergaster

If there was reason to doubt the Homo affiliation of the earliest finds, the same cannot be said of Homo ergaster, the third species of early Homo listed on Figure 1, which makes its appearance on the landscape at 1.8 million years ago in east Africa. This hominin species is quite distinct from other early members of Homo, with considerably expanded crania that had straighter walls, greater vertical height and the appearance of very large eyebrow ridges.

The first cache of these specimens were discovered at Koobi Fora near the shores of Kenya’s Lake Turkana (on the northern border of Kenya) in the 1970s, the most notable of which were KNM-ER 3733 and KNM-ER 3883 (Figure 3).

The greatest change that Homo ergaster had attained over their precursors, however, was not known until the 1985 discovery, at Nariokotome, near Koobi Fora, of a twelve-year-old adolescent, who had the misfortune of falling into a swamp, only to be swallowed up and buried for over 1.5 million years. This find (Figure 4) is one of the most intact hominin fossils in existence, consisting of an individual that is 70% complete.

When we are born, our arm and leg bones are a mix of bone and cartilage, similar to what we have in our nose. As we grow, the cartilage is replaced by bone, which spreads from the middle to the ends of each bone, with the ends “fusing” just before adulthood. This is why it is very easy for us to break bones in childhood. Using the timing of these changes, we can determine how old an individual was at the time of death. In the Nariokotome skeleton, the ends of the bones of the arms and legs (long bones) were not yet fused, indicating that this individual had not reached adult status. The discoverers (Brown, Harris, Leakey, & Walker, 1985) estimated that his adult height would have been nearly six feet. This is significantly greater than the height of any known australopithecine or Homo habilis individual.

It also presents us with the first concrete example of a fossil hominin that has fully modern stature and proportions (Tattersall, 2007). While one can see traces of an arboreal past in australopithecines and even in the earliest Homo in the form of curved hand and toe digits and slight elongation of the arms, relative to the legs, (Rightmire, 1993) by the time of H. ergaster, such traces are gone.

At present, there are eight specimens of Homo ergaster as for which skull and jaw remains are present (Strait, et al., 1997). Many other specimens are represented by scattered teeth.

The Acheulean Tool Tradition

Just slightly after H. ergaster appeared on the landscape, a different style of stone tool technology, the Acheulean (Figure 5) also appears. This is based on the hand axe, which would serve as the technological staple for the next million years. These tools were more advanced than theOldowan scrapers and are recognizable from site to site. Foley and Lahr (2003) suggest that these tools were developed during the tenure of H. ergaster and, at the beginning of this hominin’s appearance, are not very different from the late developed Oldowan tools. Several hundred thousand years following the appearance of H. ergaster, however, the Acheulean tool industry had become standardized. Rather than simple choppers, these tools demonstrate complex bifacial working and the process of “knapping” or using other rocks to create a finished tool.

The Rise of Humanity?

The presence of the Acheulean tools, the morphological changes and the increase in stature of Homo ergastersuggest that significant changes were occurring in the ways that hominins were utilizing the landscape around them and evolving in response to it. Based on analysis of the Developed Oldowan culture, Osvath and Gärdenfors (Osvath & Gärdenfors, 2005) argue that in H. ergaster, one can see evidence of anticipatory cognition, a trait only present in humans:

…we identify the niche as consisting of stone tool manufacture, of transports over long ranges of tools as well as food and of the use of accumulation spots. Our main argument is that this niche promoted the selection for anticipatory cognition, in particular planning for future goals. Once established, anticipatory cognition opened up for further cultural developments, such as long ranging migration, division of labour, and advanced co-operation and communication, all of which one finds evidence for in Homo ergaster/erectus.

Similarly (Isaac & Isaac, 1977), in a study of the African site of Olorgesaille, discovered hundreds of Acheulean tools associated with large animals, many of which had cut marks on them. Such evidence has also been found at Acheulean sites in the Middle Awash River Valley. Further, there is evidence that there was transport of raw materials from site to site, sometimes in excess of 100 kilometers. Wang and colleagues suggest that there was increased selection for longer legged individuals partly as a result of increased need for this longer transport (Wang et al., 2004). Given that there is a clear increase in brain size for these specimens over their Homo habilispredecessors, it is tempting to suggest that there was positive selection for both an increase in brain size and body size for Homo ergaster. (see side bar for more detail)(Aiello & Wells, 2002) and, as a result, hunting may have begun to play a role in subsistence. An example of a study which explores this is the paper by (Bramble & Lieberman, 2004) which examines the success of humans at endurance running. Since that success can be correlated with certain identifiable skeletal features, it appears that hominins became capable of endurance running about 2 million years ago. (see side bar for abstract from their paper ) This kind of subsistence pattern is not very different from modern-day African Bushman populations and suggests strongly that these hominins were acting in ways that were noticeably human.

Judged by several criteria, humans perform remarkably well at endurance running, thanks to a diverse array of features, many of which leave traces in the skeleton. The fossil evidence of these features suggests that endurance running is a derived capability of the genus Homo, originating about 2 million years ago, and may have been instrumental in the evolution of the human body form.

#Out of Africa (The First Time)

One of the persistent questions involving paleoanthropological research is the timing of that first migration out of Africa. Work by several researchers beginning in the 1890s had uncovered remains of hominins in both East and Southeast Asia, but because of problems understanding exactly how remains decayed or were preserved in those environments, very few concrete dates could be determined. In Europe and the Near East prior to the 1980s, there were no early hominin remains that could be dated older than 500 thousand years.

 

Transitional species?

Beginning in the summer of 1999, however, the remains of six individuals—including two remarkable partial skulls, or crania—were recovered from a hilly location at the site of Dmanisi in the Republic of Georgia (see map, below). One surprising characteristic of the skulls was their primitive appearance (Figure 2). Their small cranial size of 800cc put them squarely within the early Homo range (modern humans skulls range between 1350 and 1500 cubic centimeters). Also notable was that from the back, the widest part of the head was quite low, just above the ear. In modern humans, the widest part is three-quarters of the way up from the cranial base. These characteristics, plus the shape of the eye sockets and cheeks strongly suggested an affinity toHomo ergaster (Gabunia et al., 2000).

Two characteristics were different from Homo ergaster, however. First, the skull bones were very thick, and second, they displayed a ridge of bone not found on Homo ergaster or any of its African contemporaries. This ridge, called the angular torus, is a defining characteristic of Homo erectus, the hominin that follows Homo ergaster. These characteristics strongly suggest that the Dmanisi hominins occupy a transitional status between these two forms.

In direct association with these hominins were stone tools of what is known as the Oldowan mode: scrapers, choppers and flakes (Figure 3). This tool kit was more primitive than what was associated with African specimens of African Homo ergaster and closer to what has been found at earlier Homo habilis sites. Based on Paleomagnetism and 40Ar/39Ar dating, the hominin remains at Dmanisi are estimated to be between 1.5 and 1.8 million years old, putting them within the historical range of African Homo ergaster. This suggests that the Dmanisi hominins may represent an earlier branching of the H. ergaster line, and that each line had its own independent evolutionary trajectory.

The appearance of this hominin this far north and at such an early date is striking because it suggests that an early form of Homo had learned to migrate long distances. It should be pointed out that this migration involved more of a change in location than a change in scenery. The environmental conditions at Dmanisi were dramatically different 1.5 million years ago than they are today, and analysis of the ancient climate for the hominin layers there indicates that it was a temperate savanna with small trees and brush (Palmqvist, Gröcke, Arribas, & Fariña, 2003).

Rapid Expansion

Apart from the Georgian Caucasus, it appears that there was also a rapid expansion out of Africa into other areas of the Old World (defined as all continental areas except North and South America and the polar regions). This began shortly after the appearance of Homo ergaster. As Figure 4 indicates, hominins first appeared in Europe, the Near East, and Asia between 1.5 and 1.8 million years ago.

Southwest Asia (The Near East)

Because of its rich religious history, southwest Asia has always been an emotionally charged region for archaeological research. Yet it is here that scientists have found evidence of early non-African Homo. Two sites have been proposed as the earliest habitation locales in the Near East: Yiron and Erq el Ahmar, both in the Jordan Valley region of Israel. However, despite yielding primitive tools, they have not produced reliable dates.

At the site of Ubeidiya, also in Israel, several levels of habitation have been unearthed that suggest a long-term occupation between 1.5 to around 1.0 million years ago. Stone tools found at Ubeidiya range in complexity from Oldowan (such as those made by late H. habilis) to Acheulean (typically associated with H. ergaster). This indicates the presence of more advanced (and slightly later) hominins than those found in Dmanisi. Unfortunately, no human remains have been discovered at this site (Bar-Yosef & Belfer-Cohen, 2001).

Another notable site is Gesher Benot Ya’aqov, which has been recently re-dated to approximately 780,000 years ago (Goren-Inbar et al., 2000). The archaeological layers there are quite rich with thousands of tools, all of which are Acheulean in nature: hand axes and cleavers along with flake tools. The material at Gesher Benot Ya’aqov reflects a much greater complexity in behavior than at earlier sites, as well, yielding evidence of a remarkable advancement: the continual, purposeful use of fire. By examining the pattern of burned artifacts, Alperson-Afil has concluded that the small-stone waste pattern at the site reflects a controlled fire-source. The author argues that, while there are places where burned and unburned artifacts overlap, there are also clusters of burned artifacts alone. Here, he suggests “that an anthropogenic [that is, man-made] fire is the agent responsible” (Alperson-Afil, 2008, p. 1735). This conclusion has been supported by Goren-Inbar et al (2004).

This innovation would have been tremendously important. Control of fire would have allowed the migration of hominins into less temperate climes, giving them access to vastly different fauna to be hunted. Fire also extends the working hours of the day by providing heat and light, and could have allowed for additional planning or continued social bonding. Another considerable advantage of having controlled fire was protection, as wild animals rarely approach an open fire. Being able to protect one’s group as well as one’s food source would have increased home range and cut down on population loss due to predators. Since fire is portable, it may have allowed early hominins to become more adventurous as they moved around.

Western Europe

Spain

In addition to the Near East corridor, there is ample evidence that earlyHomo made the trek across North Africa and crossed the straits of Gibraltar. In Spain, the partial remains of a hominin jaw (Figure 5) and a lower premolar were found at the site of Sima del Elefante, near the town of Atapuerca.

This location will figure prominently into the discussion of the appearance of archaic Homo sapiens. These remains are clearly of hominin origin and share similarities to the remains from Dmanisi, but their fragmentary nature precludes a detailed exploration of how they relate to those at other sites. In addition to the hominin fossil remains, stone tools of a pre-Acheulean variety were found. These consist of flakes and scrapers and show little complexity beyond that found at Dmanisi (Carbonell et al., 2008). Paleomagnetism, cosmogenic nuclide dating, and the presence of distinctive fauna put the date of these remains and artifacts at between 1.1 and 1.2 million years ago.

At the site of Orce, in southern Spain, tools were discovered similar to those at Sima del Elefante and Dmanisi, but none of them were Acheulean. Following Gilbert and colleagues’ (Gibert et al., 1998) analysis of tools and other evidence, we know that humans were present in the area around 1.5 to 1.6 million years ago, but we do not know who they were.

Italy

Evidence for the earliest settlements in Italy has also been discovered in the last decade. At the site of Pirro Nord, a small collection of flakes and scrapers was found at a karst level dated between 1.3 and 1.7 million years ago by biostratigraphy and palaeomagnetism (Arzarello et al., 2007) (Figure 6). As with the Dmanisi site, from the kind and numbers of animals and plants found at the archaeological levels, the environment was open and dry. Once again, we know hominins were there, we just don’t know what they looked like.

The trek to the north of Europe appears to have taken more time, and the earliest archaeological material in Germany—an almost-intact lower jaw discovered in a sandpit—is dated between 0.7 and 0.5 million years ago. Travel to this area of Europe may have been hindered by the presence of ice. Northern Europe was often impassable during much of the Pleistocene because of glacial advances and there may simply have been no way to get there until the Donau-Günz interglacial, beginning around 700,000 years ago. That first discovery representing early Homo occurred at the site of Mauer, in Heidelberg, and is dated to approximately 500,000 years ago. When found in 1908 it was given the name Homo heidelbergensis, but it has since been reclassified as Homo erectus, a form that we will discuss in detail in the next post.

Who Were These People?

One of the frustrating things about fossil hominin studies in Europe is that we have only small amount of human remains to work with. Any reconstruction requires some guesswork based on what we uncover. But from skeletal material in the Russian Republic of Georgia, at the Dmanisi site, it is clear that these hominins had evolved beyond the basic Homo habilis form. Though we do not know exactly what they looked like, we have a wealth of evidence about their migration patterns. Hominins similar to these dwelled within Spain between three and five hundred thousand years later, and they were also found in the Near East. These discoveries come not just from limited skeletal material but also from abundant archaeological material of other kinds.

It is unfortunate that we do not have more material to work with, but the discoveries of the past thirty years have greatly advanced our understanding of pre-human history. As we shall see in the next section, the story of early Homoin Europe and the Middle East reflects only part of the hominin journey; for in addition to migrating north and west, they also traveled east.

#Homo erectus in Asia

Discovery

Eugene Dubois

It was 1890 and Eugene Dubois was tired. He had searched everywhere in Sumatra for the human ancestors that were supposed to be there—at least according to the theories of his mentor, famed German naturalist Ernst Haeckel. Instead, he had found only heat and malaria.

13 years before, in 1877, Dubois had arrived in Amsterdam to study medicine, but always harboring a desire to study the ancestry of modern humans. So, after four years at the University there, he accepted an invitation to go to the University of Utrecht to study comparative anatomy and devote himself to the latest thinking about the origins of the human species. It was during his time at Utrecht (from 1881 to 1887) that Dubois became enamored of Haeckel’s views on human origins, which differed from those of Darwin. While Darwin argued that humans had evolved in Africa, the region in which our closest living relatives—the chimpanzees and gorillas—still live, Haeckel believed that the origins of humanity lay in East Asia. This was so, he believed, because of his own observations of gibbons that walk bipedally when on the ground.

Haeckel also believed that there had once been a large landmass called Lemuria between the continents of Africa and Asia. In his view, Lemuria had since become submerged, leaving the modern islands of Madagascar and the East Indies as its only remains. The idea of submerged continents was not unusual for the late 19th-century, as people struggled to understand the character of biological diversity present in the world and why there were such striking similarities between animals that were geographically dispersed. The geographical distribution of marsupial fossils in South America and Australia is an example of this sort of problem, and one that was not solved until the second half of the 20th century when continental drift reconstructions suggested that ancient marsupials had used Antarctica as a conduit between the other two continents. Not only did such theories make sense of modern distributions, they were confirmed with later discoveries of marsupial fossils in Antarctica.

In any case, in 1888 Dubois joined the army and set out for the Dutch East Indies to pursue his ideas. For the next two years, he would comb Sumatra attempting to locate the hominin remains that Haeckel promised would be there. In hindsight, what Dubois was attempting was something that had never been done before: discovery of hominin material through the tools of archaeological excavation. Up to this point, all of the human fossils had been found on the surface, eroding out of the side of a bank, or as a result of farming. It had not occurred to anyone to go looking for human ancestors.

Now, with his supply of prison workers dwindling due to desertion and fever, he had almost run out of options and was on the verge of failure. Using almost all of his remaining resources, he decided to abandon his excavations on Sumatra and turn to the nearby island of Java. Emboldened by the fact that early modern human fossils had been discovered there (at Wadjak), he arrived and settled in at Trinil, on the banks of the Solo River, in 1890.


Figure 1: Dubois’ Pithecanthropus erectus

The very next year, Dubois’ long-standing efforts were finally rewarded, first with the discovery of a skullcap (calvaria) of a hominin cranium, and then with an intact femur (Figure 1). Judging by what he knew of cranial anatomy, Dubois estimated that the skull would have been approximately 900 cubic centimeters (cc) in volume, placing it below even the lowest threshold of modern humans. Further, he noticed that it was not like modern humans in shape, being too long and low. He concluded that it showed “evidence of a form intermediate between man and the anthropoid apes” (Dubois, 1896). Dubois envisioned a sequence of forms in which the gibbon gave rise to a form of chimpanzee called Anthropopithecus sivalensis, which then gave rise to the form represented by the Trinil remains, after which Homo sapiens arose (Turner, 1895).

Dubois spent the next twenty years on the road with his find, trying to drum up support for its place in human prehistory. As with Raymond Dart’s discovery of the first australopithecine thirty-three years later, Dubois did not receive a warm reception. Most critics simply said that he had gotten it wrong and that the femur did not belong to the same individual as the obviously-primitive skull cap. Some of the criticism Dubois suffered could have been mitigated had he been more open to sharing the Trinil materials; but, instead, he allowed very little access to the bones, so that very few people knew exactly what they looked like. Adding to Dubois’s credibility problems was the 1911 “discovery” of Piltdown. This intentional hoax turned the paleoanthropology world on its head for forty years, sending researchers down innumerable rabbit holes. As I noted in a previous post, the Piltdown remains made all of the other hominin finds appear too “ape-like” to be on the road to humanity and informed many opinions about finds such as those from Trinil.

On the other hand, some critics of Dubois’ new hominin claim were vicious, and questioned both his academic abilities and his judgment (Shipman & Storm, 2002)—in addition to the interpretation of the find itself. It was in reference to Dubois’ work that the term “Missing Link” was first used with reference to a particular human fossil, originating with Charles Lyell (1863) and describing palaeontological gaps. And ironically, it was in one of the most stinging criticisms of Dubois’ work that the name that would eventually stick was first used: “Homo erectus.” Eventually, many other finds in the same general area and across Southeast Asia demonstrated that what Dubois had found was a real, previously-unknown hominin form, and the first to colonize the Asian continent and the islands leading off towards Oceania.

Homo erectus across South East Asia

Figure 2: Sangiran 17

Sangiran

The earliest point at which Homo erectus appears to have begun to colonize the greater East Asian region is around 1.8 million years ago, represented first by the partial child’s skull found at the site of Modjokerto, and then, at around 1.66 million years ago, at the site of Sangiran, in Trinil, where Dubois had made his landmark discovery. This site was rich, yielding the remains of many crania, perhaps best represented by Sangiran 17 (Figure 2), an almost complete skull.

The material from the Sangiran site is very diverse morphologically, with some crania having capacities of as little as 700 to 800 cc, and other, larger heads with volumes in the range of 1000 cc. As with the late Homo ergaster finds from Africa, the remains from Sangiran yielded crania that were still widest at their bases, possessing large brow ridges. Some have thick cranial bones and are very robust (Sangiran 4), while others are very gracile (Sangiran 31). What this variation means is not clear, but most workers believe it represents a very diverse diachronic population (that is, one group living and moving around over a long period) rather than separate species inhabiting the area. The Sangiran site yielded fossil material in an almost continuous succession from approximately 1.66 million years ago to less than 800,000 years ago.

Because the area of the excavations—the Sangiran Dome—is a volcanic deposit, the layers have been securely dated by the 40Ar/39Ar method, although questions remain about the historical sequence and distribution of other animals that lived there through the ages (its faunal succession). The problem is that many of the fossils were not found in context, and relating them directly to the stratigraphy is tenuous. Despite this, most workers are comfortable with the earliest hominins in the region being at least 1.5 million years old.

One of the things hampering workers in this region is the comparative paucity of recovered stone tools. Those that have been found suggest a technological stage similar to the late Oldowan design, equivalent to that being created by the Homo ergaster populations inhabiting the area of Dmanisi and East Africa. Unfortunately, none of the tools have been associated with the hominins directly so it is not exactly clear who made them.

Figure 3: Sambungmacan 3

Sambungmacan

Another major find from the area where Dubois brought Homo erectus to light is the cranium from the site of Sambungmachan. This skull was reportedly found in 1977 but was then illegally sold to the antiquities market, where is spent considerable time in different collections before being “rediscovered” in 1998—in a New York nature curio shop called Maxilla and Mandible, Inc. (Delson et al., 2001). This was an almost-complete calvaria (Figure 3), with only part of the base missing. It is equivalent in size to the fossils from Sangiran, with a cranial capacity of around 1000 cc. It has a large brow ridge extending all of the way across the top of the eyes, a long, low cranium with a sloping forehead and a maximum width near the cranial base—all features that are also characteristic of the late African H. ergaster and Sangiran crania. Although we will never know exactly how old this cranium is, its morphology is consistent with that of the material from Sangiran.

Figure 4: Ngandong 6

Ngandong

Later in time, but also located on the Solo River, is the site of Ngandong, excavated by Oppenoorth in the early 1930s. At this site, fourteen calvaria have been discovered, all of which show advanced Homo erectus characteristics: long and low in shape, with thick-bones and a distinctive brow-ridge. (Figure 4). As with the other Indonesian finds, dating the Ngandong material has been problematic. The deposits at the site were originally thought to be around 100,000 years old, but this interpretation was turned on its head in 1996, when Swisher and colleagues claimed that the deposits were no older than between 27,000 and 53,000 years old (Swisher et al., 1996). These age estimations were made on the associated fauna, however, and as Rainer Grün and the late Alan Thorne pointed out, the faunal material does not match the skulls either in color or in texture and is likely not from the same time. Recently, Swisher and colleagues revisited the dating of the site and derived internally-consistent dates of at least 143,000 years before the present (Indriati et al., 2011). As with the Trinil remains, however, there are no associated stone tools.

Homo erectus in China

The Chinese Homo erectus material is very widely scattered and working in the region has presented many difficulties for researchers in terms of transport, language barriers and funding. Consequently, we know less about this region and its previous inhabitants than we do about most other areas of the Old World. Although there are between ten and fifteen sites that have yielded Homo erectus material, I will only touch on the most important ones.

Figure 5: Lantian

Lantian

In the early 1960s, a cranium and mandible were found in the cave of Lantian, Shaanxi province, whose characteristics matched other remains from China designated as Homo erectus. Paleomagnetic dating has yielded a date no earlier than 1.15 million years ago for the skull, with the consensus being that it is around 800,000 years old. A date of approximately 650,000 years before the present was derived for the mandible. The cranium is heavily encrusted and suffered from postmortem deformation (Figure 5). When reconstituted, it was found to have a capacity of around 780 cc (low for Homo erectus) and the bones on the sides of the head are the thickest yet recorded. At this site some flake tools, mammal remains, and an ash deposit were all recovered, suggesting hunting and control of fire.

Figure 5: Hexian

Hexian

Another almost-complete calvaria was found at Longtandong cave in the province of Hé Xiàn, dated to between 400,000 and 500,000 years ago. This find exemplifies typical Homo erectus in many ways in that it is long and low, with heavy muscle markings toward the base and the rear of the skull (Figure 6). The cranial capacity is around 1000 cc, a third-again greater than that of the Lantian calvaria. Its cranial shape is very similar to those found in Southeast Asia, suggesting that it straddles the Southeast Asian and Chinese boundary.

While both Lantian and Hexian were significant finds, another site in China boasted the single largest collection ofHomo erectus fossils ever found at one site, as well as presenting one of the greatest mysteries in paleoanthropology. In the conclusion of our look at Homo erectus in Asia, we’ll peer into the Zhoukoudian caves and consider how this species fits into the lineage of man.

Zhoukoudian

In yesterday’s post, I discussed Eugene Dubois’ 1891 discovery of Homo erectus in Java, and some of the subsequent discoveries of other remains throughout Southeast Asia and into China. Today, we’ll look at the Zhoukoudian site, which contains perhaps the largest Homo erectus cache of fossils in existence at any one site. Not only did the caves provide a remarkable number of remains, it also provided one of the greatest mysteries of paleoanthropology.In the late 1920s, vertebrate paleontologist Davidson Black, who was working at the Cenozoic Research Laboratory, began an excavation in the hills outside what was then known as Peking (now Beijing). Local townsfolk had brought Black bones to him that they claimed were those of “dragons.” These turned out to be extinct fauna. Quickly, Black discovered some hominin mandibles, some cranial fragments and one complete calvaria. He named the new species Sinanthropus pekinensis, or Chinese man from Peking. Black continued the excavations until his death in 1934, whereupon Franz Weidenreich was brought in. A trained anatomist who had just finished up a visiting professorship at the University of Chicago, Weidenreich found an additional five complete calvaria as well as several partial crania and fragments. He immediately recognized similarities between what Dubois had unearthed and what was being found at Peking: individuals with long, low crania, large brow ridges and large faces.Weidenreich continued to excavate through the mid-1930s, but in 1937 the Japanese invaded the north part of the country and many Chinese fled south to escape the oncoming armies. Sensing that the trouble would eventually reach Peking, Weidenreich readied all of the material for transport out of the country: he completed high quality plaster casts of the fossil remains and took them with him to New York. The original fossils he locked away for safekeeping.In 1941, as conditions in China continued to deteriorate, the decision was made to move the original fossils, which were placed in a set of footlockers and given to a garrison of U.S. solders stationed in Peking. The plan was for them to be transported to the port city of Qinhuangdao, where they were to be loaded onto the U.S. Benjamin Harrison. What then happened is not entirely clear. The Japanese army captured the garrison of marines and the bones seemingly vanished. No one ever saw them again, and to this day the whereabouts of the fossils remain a mystery. Some believe that they went back to Japan with the Japanese army, others think that they became scattered among the local inhabitants of the area, and still other suggest that they ended up at the bottom of the ocean, never to be seen again. In 2005, the Chinese government began a program to locate the original bones.Figure 7: Five of the Zhoukoudian Crania

The Zhoukoudian site yielded an amazing amount of material: twelve total crania of which six were almost complete, as well as a large collection of mandibles and hundreds of cranial fragments (Figure 7). The cranial capacity of these individuals ranges from 915 to 1225 cc, making them larger than the majority of the Southeast Asian individuals. But nearly as important as the fossils themselves, researchers found numerous stone “cleavers” and four layers of ash, reflecting the use of fire. All in all, there seems to have been a continuous occupation of the cave from around 600,000 to 200,000 years ago, spanning thirteen layers and some forty meters of deposits. Along with the crude implements, hundreds of mammal species are represented by remains in the cave, many of the bones having distinctive cut marks on them. This suggests that the occupants of this cave could (and did) hunt many different species for food.

Homo erectus and the Hand Axe

While the archaeological record of tools for the Southeast Asian Homo erectus sample is extremely thin, some Chinese sites have provided artifacts. (Schick & Zhuan, 1993). Uniformly crude and not as developed as the Acheulean mode tools in East Africa, these bifacially-worked chopping tools have been referred to as “cleavers” by some researchers (figure below). There is considerable variation in size and shape, however, and Lycett has argued that there are regional variations in biface design and construction that can be attributed to the demands of different environments (Lycett, 2008). Interestingly, it is also clear that, over time, these tools became more uniform, resembling the hand axes that are found elsewhere. This suggests two strong possibilities: first, that specific functional necessities were the driving force behind their shape, and that these functional constraints necessitated a similarity in design between groups; or, second, that “technology swapping” between populations was occurring.

Figure 8: Bifaces from Zhoukoudian

Although these “cleavers” appear in numerous places in the Chinese record, there is a sharp break between them and the well-made hand axes of Africa, Southwest Asia and the Indian sub-continent. This break is referred to as the “Movius” Line, named for the researcher who first noticed the pattern. It has always been a source of puzzlement to archaeologists, but recently, some researchers have suggested that this demarcation exists because the Chinese Homo erectus populations possessed a raw material alternative for creating the complex tools they needed: bamboo. Bar-Yosef and colleagues have shown that with less effort and time required to make them, bamboo points can be created that are nearly as strong as and easier to use than stone ones (Bar-Yosef, Eren, Yuan, Cohen, & Li, 2012).

Beyond Homo ergaster: How many species of Mid-Pleistocene Homo?

One of the persistent problems of hominin studies when we get to our own line is attempting to determine how many species coexisted. As we have seen previously, there was even disagreement about how many species were represented in Eastern Africa, with Homo rudolfensis and Homo ergaster.

Historically, many archaeologists have held that Homo erectus was the hominin that colonized the Old World, and that this colonization took place between one and two million years ago. During the 1970s and 1980s, paleoanthropological thought held that Homo habilis followed the reign of the australopithecines, and was in turn followed by Homo erectus. More recently consensus has emerged around the idea that there was further speciation in those populations that ended up in Europe and Asia. Whether one accepts one species (H. erectus) or two (H. erectus and H. ergaster), there is, as Ian Tattersall describes, “a relatively cohesive subset of the family Hominidae.” (Tattersall, 2007)

Indeed, one is struck by the unity in morphological features that make up Homo erectus/Homo ergaster in all parts of the Old World. Rightmire (Rightmire, 1998) has consistently argued that the traits used to differentiate Homo ergaster from Homo erectus are lacking and that it is best to simply use the name Homo erectus to describe all of the middle Pleistocene hominins between about 1.6 million and 300,000 years ago. Antón suggests the following traits that characterize the species as a whole: a cranial vault ranging in volume from approximately 700 to 1200 cc; a low, sloping forehead and sharply angled rear; a large, single brow ridge over the eyes; and sharp muscle markings on base of the vault with very thick cranial bone. (Antón, 2003).

Cranial morphology is remarkably static through time as well (Kidder & Durband, 2004), with little change for hundreds of thousands of years. Differences that are found do not constitute trait polarities (presence or absence of a particular feature), but are differences in overall dimensions within a consistent general type, such that it is reasonable to assign these distinctions to regional genetic drift.

On the other hand, Wood has made the argument that, while it is reasonable to assign the taxon Homo erectus to the material in Asia, it is not reasonable to do so for the African remains: the Asian samples are marked by the presence of traits such as the sagittal keel (a ridge of bone on the top of the head, visible on Figures 1 and 4), the angular torus and thick cranial bone, while these features are not as evident in the African examples. Wood has suggested that the earliest fossils from Africa—originally designated Homo erectus—be called Homo ergaster, instead, a convention I adopted for the previous post in this series. At some point, however, a group or groups left Africa with some of these traits present, and the best explanation for their presence in both the Chinese and South East Asian populations is shared retentions from an ancestral population.

Homo erectus and the Created Order

Figure 9: Zhoukoudian Homo erectus and
Australopithecus africanus

At some point we must consider Homo erectus from another perspective, as well. It has been argued by those opposing evolution in general and human evolution in particular that the australopithecines represent nothing more than aberrant apes (Morris, 2002). While such an argument does not bear up under scrutiny even with regard to australopithecines, itcertainly cannot be used to describe Homo erectus in light of the extensive material we have for this species. Not only is Homo erectus morphologically stable through time and across geographical space, it is also clear that these hominins are considerably more advanced than australopithecines (Figure 9). The crania of Homo erectus are longer, higher and considerably larger in volume; the face is more pulled in and less scooped. These are individuals that are creating complex stone tools, which are economical and efficient. In China, they are also controlling fire, an invention that completely changes how the day may be organized, and also expands the repertoire of what is edible. There is evidence for the controlled use of fire at both Lantian and Zhoukoudian and, considering the evidence at Gesher Benot Ya’aqov, it appears that as Homo erectus moved east, they brought fire with them.

While not completely human, it is clear that Homo erectus were hominins practicing many of the behavioral patterns that we identify as human, and were getting closer to being human.

#The Rise of Archaic Homo sapiens

Beginning around 1.6 million years ago, the first large-brained hominin appeared on the landscape. This was Homo ergasterHomo ergaster had a modern skeleton and more advanced food-gathering methods than previous hominins. It was also the first hominin to make it out of Africa, its earliest remains having being found in Dmanisi, in the Republic of Georgia and, a bit later, in several places in southern Europe.

Our best understanding is that this form gave rise to Homo erectus around a million years ago, and that by 700,000 years ago, Homo erectus was firmly established as the dominant (if not the only) hominin on the landscape. From the river valleys in Indonesia, to the open savannas in Africa, to the caves in China, India and Europe, this hominin had mastered fire, standardized stone tool technology and incorporated hunting into its daily life. Through the approximately million-year heyday of Homo erectus, the Acheulean tool technology—focused on the hand axe—remained unchanged. But, yet again, change was on the horizon: beginning around 600 to 700 thousand years ago, new hominin forms appear in the archaeological record, all having certain common characteristics that represent advancements over those found in Homo erectus. These were the first, still-archaic Homo sapiens.

Cranial capacity in these new hominins increased from the Homo erectus average of 900 CC3 to an average of 1100 CC3, with the heads becoming larger and more vaulted. The maximum cranial width was now midway up the sides of the vault, rather than near the ears as was the case with Homo erectus. In fact, some of the archaic Homo sapiens crania are among the largest skulls found. Faces are also larger; as are front teeth, and the faces do not project out as much as with prior types, having a more orthognathic (flatter) appearance. The extensive brow ridges—which formed a continuous bar in Homo erectus—are now divided in the middle, above the nose. As with every other stage of human evolution, we must start with the primary fossil remains before discussing their taxonomic status; and that means beginning with the record preserved in Africa.

Africa

Figure 1: Bodo (from Bräuer, 2012)

As Bräuer notes (Bräuer, 2012), hominins that are distinctly different from their Homo erectus precursors appear on the landscape in Africa between 600 and 700 thousand years ago. While only a partial cranium, the find of Bodo, in east Africa, possesses the largest face of any hominin yet recorded. This individual has alternatively been described as “developed Homo erectus” and “Early Archaic Homo sapiens,” and has been dated to around 600,000 years ago (Figure 1). Despite its size, this cranium represents a shift toward a form in the direction of modern humans; a less scooped face, a brow ridge that is now separate rather than one continuous bar, and a cranial capacity of slightly over 1300 CC3.

Figure 2: Kabwe (Cast)

Perhaps one of the most famous (and complete) skulls that has ever been discovered came from the Broken Hill mine in what was then known as Rhodesia. Known for decades as Broken Hill 1 (Figure 2), it is now more commonly called Kabwe. This is a visually stunning skull, with a very large face and enormous brow ridges. The cranial capacity is around 1100 CC3 and the head is sloping and long. This cranium is thought to be around 300,000 years old. Very similar to Kabwe, at least in cranial morphology, is the find from Saldanha (Figure 3). This has a low, sloping forehead, large supraorbital tori and a very sharply-angled rear of the vault. It has been estimated to be around 400 thousand years old.

Figure 3: Saldanha (Cast)

 Saldanha

From the site of Laetoli, which yielded the phenomenal footprints of one of our earliest ancestors, Australopithecus afarensis, comes a cranium described by Magori and Day (1983) as “…Homo sapiens but of an archaic variety” (Figure 4) This skull shows many similarities to Saldanha and Kabwe, being long and low with prominent brow ridges. The date for this hominin places it late in the sequence (120,000 plus or minus 30,000), but this date is based on an assumed correlation with beds at Olduvai and may not be correct. While it is clearly archaic, an associated face shows considerable reduction in size, toward the modern condition, suggesting that, at least for some populations, selection for smaller facial features was occurring and did not go in concert with comparable changes in the vault.

Figure 4: Laetoli Hominid 18 (From
Magori and Day, 1983)

Laetoli Hominid 18 (From Magori and Day, 1983)

This pattern is also evident in a find from North Africa, from the Atlas Mountains of Morocco. Here was unearthed the Jebel Irhoud (or Ighoud) 1 cranium (Figure 5). Dated to approximately the same time as the given date for LH18, this cranium still has quite prominent brow ridges and is long and low but the face is considerably reduced and pulled in under the forehead.

 

 

Figure 5: Jebel Irhoud 1

Figure 5: Jebel Irhoud 1

It is clear that African post-Homo erectus morphology was in a state of flux for some time—possibly several hundred thousand years, judging from the wide morphological variability that we find. It is this variability that had led many researchers to use the “archaic Homo sapiens” designation (see below), since the task of drawing relationships based on derived and primitive traits has revealed few clues in the overall evolution of these hominins. We know that they are getting more modern over time because we see this in individual skulls but the overall pattern is difficult to quantify.

It must be remembered that, for most of this time period, the variability that we speak of is seen in the cranium. This is for two reasons: first, remains other than the cranium are scant and often fragmentary; second, what we do have of such post cranial remains are not appreciably different from anatomically modern humans. At approximately one million years ago, our ancestors attained what is basically a modern skeleton. These hominins are obligate bipeds, some are between five and six feet tall, and their bone structure is modern.

Europe

Figure 6: Gran Dolina Material

Figure 6: Gran Dolina Material

In recent decades, there has been a bit of a renaissance of work in Europe and many critical discoveries have been made that shed light on the evolution of these forms and the origins of perhaps the most well-known variant of archaic Homo sapiens, the Neandertals. One of the most impressive fossil hominin and archaeological sites in Europe comes from the town of Atapuerca, in northern Spain. This site contains material stretching from just over a million years ago down to 300 thousand years. Discovered in 1981, the Atapuerca cave system contains three major sites, the Gran Dolina, the Sima del Elefante and the Sima de Los Huesos. Systematic excavation turned up stone tools in 1991 (Rodríguez et al., 2011). Of particular note, however, was the huge quantity of human fossil remains that stretch for almost the entire vertical distance at the site. Morphologically, these hominins are quite varied. The Gran Dolina cave, which is the earliest of the group, yielded hominin remains that date to around 800,000 years ago. These remains (Figure 6), which consist of cranial, facial and dental materials, suggest a mix of primitive and modern traits. The dentition is large, a carryover from Homo erectus, while the facial skeletons show some modern characteristics in that parts of the face are everted, as in modern humans. Other characteristics are derived in the direction of Neandertals, however. The nasal bones stick out, a trait not found in Homo erectus. This combination of traits has led the researchers to hypothesize that these remains reflect the last common ancestor to modern humans and Neandertals (Arsuaga et al., 1999). It is not clear at present, though, that we can say for sure what the morphology of these hominins represents.

 Figure 7: Atapuerca 5

Figure 7: Atapuerca 5

Further up in time come the remains from the site of Sima de Los Huesos. These remains are likely between 300 and 400 thousand years old. According to the describers of the fossil skeletal material found there, these remains “document an early stage of Neanderthal evolution.”(Arsuaga, Martinez, Gracia, Carretero, & Carbonell, 1993). Among the over 4000 remains found at the site are two complete and one partially complete skull (Figure 7). The skulls are notable for their massive brow ridges and faces. Further, the facial skeletons are quite unlike that found in the Gran Dolina. These skulls are characterized by what is known as midfacial prognathism, a trait exemplified by the later Neandertals. It is as if someone has grabbed the nose and pulled the face out from the middle.

Figure 8: Ceprano

Figure 8: Ceprano

Another find of great antiquity in Europe comes from the site of Ceprano, (Figure 8) midway between Rome and Naples, in Italy. It is a partial cranium with associated crude bifaces that are little more advanced than the Developed Oldowan tools crafted by the hominins that preceded it (Ascenzi, Biddittu, Cassoli, Segre, & Segre-Naldini, 1996). This hominin has been dated to around 800,000, placing it half a million years after the archaeological material at Pirro Nord.

 

 

Figure 9: Petralona (Photograph by David Brill)

Figure 9: Petralona (Photograph by David Brill)

One of the most important finds from Europe comes from the site of Petralona near the town of Thessaloniki, in Greece. Discovered in 1960, this is one of the most complete fossil human crania in existence and has an estimated cranial capacity of over 1200 cc. This skull is very large and long, with a sloping forehead, large eye orbits and rugose (ridged and wrinkly) features. In many ways, it is a dead ringer for SH5 from Atapuerca, having a very pneumatized (puffy) face that is pulled out from the midline of the skull and very strong brow ridges (Figure 9). These similarities suggest a generalized pan-European form between 300 and 500 thousand years ago. Like the Atapuerca skull, this one has what can be called “incipient” Neandertal morphology and, given that Neandertal remains have been found in the Greek isles and in nearby Italy, it is reasonable to suggest that there was widespread positive selection for these traits. Any gene flow between these populations would have further reinforced these changes.

Figure 9: Petralona (Photograph by David Brill)

Figure 9: Petralona (Photograph by David Brill)

From Germany come two more important finds: the Mauer mandible and the Steinheim calvaria. The Steinheim find is considerably smaller than the Petralona individual and is very gracile in appearance. The skull is quite fragmentary, having been crushed postmortem (Figure 10). Like many of its contemporaries, it has a long, low skull. It does, however, show general rounding of the back of the cranium and a more flattening of the face.

 

 

 

Figure 11: Mauer Mandible

Figure 11: Mauer Mandible

The Mauer mandible is large, suggesting a massive individual. It has no clear Neandertal traits, instead resembling a generalized archaic Homo sapiens form. Discovered in 1908 during a mining operation, this find has been dated at around 500,000 years (Figure 11). Like the Steinheim skull, though, it has characteristics advanced over Homo erectus, with teeth intermediate in size between that form and the Neandertals that followed. It is this fossil that is the hypodigm of Homo heidelbergensis—that is, the sample from which the characters of that population is to be inferred.

Figure 12: Arago

Figure 12: Arago

From France comes the important skull from the site of Arago (Figure 12). The cranial remains consists only of the face and frontal bone (the rest has been reconstructed on the figure to the left) but the face is relatively undistorted, revealing a morphology similar to that of SH5 from Atapuerca and Petralona, with heavy brow ridges and large maxillary sinuses. A mandible and partial pelvis were discovered along with the cranial remains. Through biostratigraphy and uranium series dating, the find is thought to be between 300 and 400 thousand years old, making it contemporary with those similar remains.

Archaic Homo sapiens: A Taxonomic Mess

One of the greatest challenges facing students of human evolution comes at the tail end of the Homo erectus span. After Homo erectus, there is little consensus about what taxonomic name to give the hominins that have been found. As a result, they are assigned the kitchen-sink label of “archaic Homo sapiens.”

Tattersall (2007) notes that the Kabwe skull bears more than a passing resemblance to one of the most prominent finds in Europe, the Petralona skull from Greece. In turn, as I mentioned above, the Petralona skull is very similar to one of the most complete skulls from Atapuerca, SH 5, and at least somewhat similar to the Arago skull.

Further, it is noted that the Bodo cranium from Africa shares striking similarities to the material from Gran Dolina (such as it is). This suggests that, as was the case with Homo erectus, there is widespread genetic homogeneity in these populations. Given the time depth involved, it is likely that there was considerable and persistent gene flow between them. Tattersall (2007), argues that, since the first example of this hominin form is represented by the Mauer mandible, the taxonomic designation Homo heidelbergensis should be used to designate these forms. This would stretch the limits of this taxon, however, since it would include the later forms from Africa as well. If there was considerable migration and hybridization between these populations, it could be argued that a single taxon makes sense. However, at present, there is no definitive material evidence for such migration, or widespread agreement on calling all these hominins anything other than “archaic Homo sapiens.”

#Archaic Homo Sapiens in East Asia

Now we progress beyond Homo erectus in East Asia, an area that, as nearly as we can tell, appears to mirror the changes that occur in Africa and Europe in documenting the transition to archaic Homo sapiens.  The catch phrase here is “as nearly as we can tell.”

When the incredible cache of human fossil remains from the site of Zhoukoudian  disappeared toward the beginning of World War II, this was not only a sizeable setback for the study of human evolution in Asia, but represented the loss of the largest cache of human remains ever discovered in this region.  That we have any information from this site is only due to the ingenuity of Franz Weidenreich in making high-quality casts of the fossils and the few remains discovered in 1966 at the same location.

If Africa was considered the Dark Continent in the glory years of exploration in the late 1800s, then Asia could reasonably be considered the Dark Continent for the study of human palaeontology, especially as it pertains to archaic Homo sapiens.  Excavations have revealed very little in China, nothing whatsoever in Japan or Australasia, and only one notable site in Indonesia.  Consequently, despite having a well-represented sequence from late Homo erectus to archaic Homo sapiens in Europe and Africa, the fossil trail between the two has grown quite cold in East Asia.

While there are more than seventy sites with Homo erectus, archaic Homo sapiens or early modern remains in East Asia, the vast majority of these consist of isolated teeth or scattered, small cranial fragments (Liu, Zhang, & Wu, 2005).  To further exacerbate the problem, there are no securely dated fossil remains between approximately 150 thousand and 30 thousand years ago.  As Brown (2001) points out, this is the time in which modern humans are either evolving or have just evolved elsewhere in the Old World.

The Fossil Evidence

China

There are only three reasonably complete crania from China that date from the time period just post-Homo erectus. These are from the sites of Dali, Mapa and Jinniu Shan and are shown in Figure 1.

Figure 1: Archaic Homo sapiens crania in China (Adapted from Pope, 1992)

Figure 1: Archaic Homo sapiens crania
in China (Adapted from Pope, 1992)

Dali

The Dali find represents a mostly complete cranium that was found in 1978 in a dating context that presented challenges for determining its age.  The surrounding sediment was originally dated to around 200 thousand years ago (Pope, 1992) by uranium series analysis but it was found with riverine deposits and heavily worn artifacts and faunal remains, suggesting that the skull had been transported and that the date may not fit the cranium. Recently, Xiao et al (Xiao, Jin, & Zhu, 2002) have reanalyzed the surrounding wind-blown strata to determine an age of the original deposits and have concluded that the remains are roughly 270 thousand years old.

The cranium suffers from slight facial distortion and is missing a large section of the right side of the skull but is, otherwise, intact.  It is long and low, with very well-developed brow ridges.  What is undistorted in the face, however, shows considerable reduction over the Homo erectus condition and the face is flat, overall.  Additionally, despite its length, there is considerable curvature at the back and the rear of the vault, which is less acutely angled.  As with other East Asian Homo erectus remains, however, the skull possesses a sagittal keel.

Figure 2: Dali Cranium

Figure 2: Dali Cranium

Pope originally suggested that this cranium exhibits traits that are reminiscent of Neandertals, a conclusion that was not well received at the time but is now being re-thought based on recent genetic information.  A recent re-evaluation by Wu and Athreya suggest that it possesses characteristics that are intermediate between Homo erectus and archaic Homo sapiens and resembles, in the sections of its cranial base, populations from Africa and Europe (Wu & Athreya, 2013).

Jinniu Shan

Discovered in 1984, a partial skull was unearthed from the site of Jinniu Shan.  Although not quite as complete as the Dali specimen, this cranium displays many of the same features as Dali and has been comfortably designated archaic Homo sapiens.  Electron spin resonance (Now electron paramagnetic resonance) dating of five fossil animal teeth reveals a date of approximately 200 thousand years B.P. (Tiemei, Quan, & En, 1994)

Figure 3: Jinniushan (From Tiemei et al. 1994)

Figure 3: Jinniushan (From Tiemei et al. 1994)

As with the Dali find, this skull exhibits advanced traits over theHomo erectus condition, including a more rounded rear and side of the vault, facial flattening, and a general thinning of the cranial bones.  Brown (2001) writes that the cranium has a volume of around 1400 CCs, just under the average for anatomically modern humans.  Archaic traits are still present, however.  There is a very well-developed brow ridge, although there is some separation just above the nose (glabella).   The cranial height is low, similar to that of Homo erectus and cranial length is similar to those of archaicHomo sapiens in Europe and Africa, being longer than those of modern humans.

Mapa (Maba)

Figure 4: The Mapa Cranium. Photo from Australian National Museum

Figure 4: The Mapa Cranium. Photo from Australian National Museum

The Mapa cranium, discovered in 1958, is not as complete as either the Dali or Jinniu Shan crania.  It has been dated by Uranium Series to between 135 and 129 thousand years ago (Brown, 2001).  It consists of several large cranial fragments that comprise the front and right side of the skull, including the region of the nose.  Of the three crania mentioned, this is the most archaic, with a broad upper face, large brow ridges and overall longer vault.  Additionally, the cranial vault bones are thicker than those of either Jinniu Shan or Dali, recalling the Homo erectus condition.

Southeast Asia

The only notable cache of archaic Homo sapiens remains from Southeast Asia come from the site of Ngandong.  Originally excavated by Oppenoorth in the 1930s, this site yielded some eleven crania, most of which were vaults.  These were discovered near the town of Ngandong on the banks of the Solo River, in what is known as the “high terrace.”  These fossils had been traditionally dated to between 150 and 200 thousand years ago but, in the late 1990s, Swisher and colleagues released a set of radiometric dates from this terrace that placed the hominins at approximately 30,000 years before the present (Swisher et al., 1996), a date that left many scratching their heads due to the patently archaic nature of the fossil material.  Grün and Thorne (Grün  & Thorne, 1997), in a later examination of the stratigraphy, state that this terrace is “a mélange” of material from different levels and sites.  As such, they contend that these layers are very hard to date chronometrically.  A recent paper by Indriati and colleagues have has suggested that these remains cannot be dated more securely than between 140 and 500 thousand years B.P.  Some stone tools that were non-Acheulean but generally post-Oldowan and Palaeolithic in nature were found in the strata and it is tempting to relate them directly to the hominins but the nature of the deposits precludes that definitively (Indriati et al., 2011).

Figure 5: Ngandong 6

Figure 5: Ngandong 6

Oppenoorth described these crania as Homo javanthropus and they were also referred to as Homo soloensis (Zeitoun, Détroit, Grimaud-Hervé, & Widianto, 2010).  One worker in the region, GHR von Koenigswald, referred to them as “tropical Neanderthals” (Bartstra, Soegondho, & Wijk, 1988).  These crania exhibit a range of traits that are progressive over the Homo erectus condition, such as slightly expanded breadths and higher vaults.  The morphology is peculiar, however, in that a number of traits present on these hominins found on the cranial base cannot be found on crania that succeed them spatially or chronologically.  Consequently, Durband (pers. comm.) has suggested that these crania represent a relic population that did not give rise to any successor groups.

Human Evolution in East Asia

Taken as a whole, these skulls clearly represent a transitional phase between Homo erectus and modern Homo sapiens, occupying the same general period of time as those from Europe and Africa, although it is harder to ascertain chronological dates for these finds.  Rightmire (Rightmire, 2007) has suggested that these fossils resemble in many ways the archaic Homo sapiens crania from Europe and Africa and that it is difficult to argue persuasively that these populations were separated to any large degree genetically.  Liu et al. (2005), as well as Pope and Wu suggest that there is a regional set of features that link the Homo erectus populations with those of the later archaic Homo sapiens in China and cite as evidence the facial flattening and the presence of shovel-shaped incisors seen in the archaic Homo sapiens crania.  Weidenreich, who examined the Zhoukoudian Homo erectus remains in depth, also saw this continuity and suggested that as many as twelve morphological features were present in the Homo erectus remains that are present in later, modern crania.  It has also been suggested independently by Pope and Wu that there are links to Neandertals in these crania, a position that has, historically, not received much support but which, with the advent of new genetic information, has received a more serious hearing.

The Genetic Evidence

In recent years, genetic studies have shed much light on the comings and goings of different groups of Homo sapiens and these studies have stretched our knowledge back beyond our own modern form and into the time of our recent ancestors.Using pseudogenes on the X-chromosome, Garrigan and colleagues (Garrigan, Mobasher, Severson, Wilder, & Hammer, 2005) have found evidence in modern humans of ancient DNA that is Asian in origin, perhaps as old as 2 million years.  This strongly suggests genetic continuity from the early Homo erectus populations through archaic Homo sapiens and to modern human groups.  This lineage has its highest frequency in the southern Chinese but can be found in all of the Asian populations sampled.  The authors write:

Any degree of dual ancestry in the modern human genome would either demonstrate that the transition to an anatomically modern form did not occur in an isolated, panmictic population (Cann, Stoneking, and Wilson 1987) or that replacement of preexisting hominid populations was incomplete (e.g., Brauer 1989; Smith, Falsetti, and Donnelly 1989).

The conclusions of Garrigan et al. have been contested by Blum and Jakobsson (Blum & Jakobsson, 2011), who argue that the ancient autosomal lineage patterns are consistent with an out-of-Africa scenario.  However, to obtain this result, the authors were required to set their effective population size to 14,000 individuals, matching the estimates produced by the mtDNA studies.  Thus, the results are only as good as the assumptions of those studies.

The general conclusions of Garrigan et al. were corroborated by Wall et al., who studied polymorphism data (Wall, Lohmueller, & Plagnol, 2009). They concluded that there is evidence for considerable mixing of ancient populations in Europe, Asia and West Africa and that this mixture represents the norm in human populations history.

The genetic link between archaics and moderns throughout Eurasia was further supported by the work of Green et al., who presented a genetic sequence of Neandertal DNA.  Their results strongly suggested that Neandertals interbred with other archaic Homo sapiens populations in Eurasia and that, because of the presence of Neandertal DNA markers in modern Asian populations, there was continuity between archaic Homo sapiens and modern Homo sapiens in Europe and Asia.

This genetic evidence is in keeping with what Macintosh once referred to as “the mark of ancient Java” that he found in modern Australasian populations (Macintosh, 1965).  Durband (pers. comm.) suggests, however, that, while there is good genetic evidence of some admixture, the fossil evidence suggests that some replacement (e.g. Ngandong) did occur.

Tying the Fossils and the Genes Together

One of the drawbacks of the current genetic studies is that it is difficult to relate them directly to the palaeontological evidence because beyond around 50 thousand years before the present, it is not possible to derive genetic information from the skeletal (morphological) material.  Consequently, while we have clear genetic data from modern individuals that indicates admixture between archaic Homo sapiens groups, we do not know exactly how that manifested itself.  If Durband is correct that the Ngandong material represent a relic population of late archaic Homo sapiens, might that also be the case for other populations in this region that are represented by some of the above crania?  Based on the general paucity of evidence in this region, we simply do not know.  All we can say for sure is that these crania represent an advanced condition over the Homo erectus populations that preceded them in this region.  How much gene flow occurred in the process of this evolution is not clear.

Archaeological Evidence

The stone tool evidence in East Asia presents an unusual picture.   In China, the tools that date to the end of Homo erectus time and the advent of archaic Homo sapiens are still choppers, chopping tools, cleavers and flakes.  Between 100 and 50 thousand years B.P., however, several caves yield a preponderance of scrapers and flake tools and these have been favorably compared to the Mousterian of Europe, produced by Neandertals (Ofer Bar-Yosef & Wang, 2012). These tools are simple, in comparison to other areas, however and they persist for a greater period of time, stretching from west China to Siberia.  It has been suggested that, as was mentioned last post, those who migrated east did not fully develop their blade tools as they did in Europe because they were able to make use of bamboo, which allowed them considerable latitude in tool manufacture, not to mention sharpness.  The presence of the simple tools has been explained in that those were required to produce the bamboo tools.  Bar-Yosef and Wang admit, however, that this explanation is only hypothetical at present and, as one travels north, out of the latitudinal range of bamboo, becomes increasingly difficult to support.

In Japan, despite the complete lack of late Pleistocene hominin remains, there are stone tool industries dating back to between 50 and 70 thousand years B.P.  These tools are characterized as being very simple, little more than cobbles and choppers for the vast majority of the late Pleistocene in Japan (Akazawa, Oda, & Yamanaka, 1980).  When they do change, they do so rapidly and there are microlithic tools found in association with bone points late in the sequence, corresponding, almost certainly, with modern human societies.

Confounding research in this area is the recent exposure of a grand hoax perpetrated by a once-renowned Japanese archaeologist, Fujimura Shinichi, who had pushed back the appearance of humans in Japan to the early Palaeolithic to between 100 and 600 thousand years B.P. Privately, it was thought that the evidence was incredible and many of us wondered (some aloud) if there was not contamination or stratigraphic intrusion.  Subsequently, he was caught red-handed by a national newspaper reporter while deliberately burying stone tools at a site in order to make it look older than it was.  He soon confessed to having done this at many sites, so as to enhance his reputation.  It is estimated by archaeologist Shuzo Oda  (pers. comm.) that as many as 90 palaeolithic sites will have to be reexamined to determine their authenticity.

Bar Yosef and Belfer-Cohen (O. Bar-Yosef & Belfer-Cohen, 2013) suggest that when the Early Würm climate in Europe became too inhospitable for the northern European Neandertals, they went south and east, bringing the Mousterian stone tool technologies with them, as is exemplified by the Middle Palaeolithic tools found at Denisova Cave, in Siberia.  These authors suggest that the Levant served as a crossroads of sorts with moderns and Neandertals meeting and interbreeding.  Current work by myself and a co-author, however, suggests that the inbreeding in this area is not adequately reflected in the morphology of the early modern humans there, who appear to show a morphology that is reminiscent of African archaic Homo sapiens, not Neandertals.

If the genetic evidence is corroborated, and there was population (and, perhaps, cultural) continuity across Eurasia, it could help to explain the similarity of cultural implements and skeletal morphology that is witnessed in the representatives of these populations.

What is clear from this evidence in this area and in Europe and Africa is that we, as modern humans have a concrete link to the past.  No longer can we look at these remains and regard them as curios.  Even if they do not completely resemble anatomically modern humans, they behave in ways that are demonstrably modern.  Furthermore, we carry their legacy in our genetic code.  The last great push into modernity was yet to come but the populations represented by these individuals were almost there.

Next, we will address the most alternately celebrated and reviled hominin form in the entire pantheon of human evolution: The Neandertals.

#The Rise of the Neandertals

A model of an adult Neanderthal male head and shoulders on display in the Hall of Human Origins in the Smithsonian Museum of Natural History in Washington, D.C. Reconstruction based on the Shanidar 1 fossil (c. 80-60 kya).

A model of an adult Neanderthal male head and shoulders on display in the Hall of Human Origins in the Smithsonian Museum of Natural History in Washington, D.C. Reconstruction based on the Shanidar 1 fossil (c. 80-60 kya).

The Discovery of the Neandertal Type Specimen

In the region of Dusseldorf, Germany, lies a valley named after the 16th century German pastor and hymn writer Joachim Neander.  Neander, it is said, roamed the valley, using its beauty to gain inspiration for his hymns, the most well known of which is Praise to the Lord, the Almighty, the King of Creation.Known far and wide for its limestone, the Neandertal or Neander “Valley” attracted the attention of local industrial groups in the early 1700s and considerable mining was carried out in this area through the middle 1800s. It was during the mining of one such area in 1856, Feldhofer Cave, that workers discovered a set of bones, which they initially thought belonged to a bear. To the local biology teacher, Johann Fulrott, who had been called in to identify them, they looked remarkably human—but not exactly. Something was not quite right. Intrigued by their form, and knowing that they represented something out of the ordinary, he took them to the city of Bonn and showed them to university anatomist Hermann Schaffhausen. After a joint investigation of the skeletal remains, in 1857 Fulrott and Schaffhausen announced to the world that they represented a new form of human predating modern Homo sapiens and with an as yet undetermined relationship with them.What they did not know at the time was that the remains from the Feldhofer Cave very closely resembled those that had been removed from the Belgian site of Engis and the Forbes Quarry site in Gibraltar several decades earlier. It was not until 1864 that these remains as a group began to be referred to as “Neandertal Man.”  (King, 1864) (Note: while this hominin form is often rendered “Neanderthal,” the “h” in the German word for valley began to drop out of usage around the turn of the 20th century, leaving the word correctly spelled “Neandertal,” today.)

Marcelin Boule and the Relegation of Neandertals to the Trash Heap of History

“NeanderTHAL!” One can hear Bill Cosby yell the word in the classic comedy routine of the same name in which the Neandertal, or “cave man” is found to be eating bushes or sneaking up behind two Sabretooth tigers and hitting them with clubs. That is only one of many derogatory references to our most recent precursors. Indeed, the notion of the stooped over, heavy-browed brute is pervasive in our society. As Dave Frayer (Frayer, 2013)notes:

The “Neanderthals are inferior” attitude traces back to their earliest descriptions in the mid-1800s when the first Neanderthal was labeled as “freak” or an “idiot” or “incapable of moral and religious conception.” For many, the discoveries after 1865 confirmed these labels. Even the majority of human paleontologists supported this view.

Beginning in the late 1800s, Neandertals began to be seen as a side-branch to modern humans—and a particularly primitive one at that. This reached its culmination with the writings of anthropologist Marcelin Boule (Figure 1), who performed the first systematic description of a Neandertal specimen in 1911 (Boule, 1911). Boule was handicapped by an almost overwhelming inability to conceive of these remains as being ancestral to modern humans in any way. Consequently, the publication that emanated from his investigation was rife with errors that it is difficult, in hindsight, to justify or excuse.

Figure 2: The Neandertal from La Chapelle-aux-Saints

Figure 2: The Neandertal from La Chapelle-aux-Saints

The La Chapelle Neandertal had been discovered in 1908 and, along with the other Neandertal remains, constituted, at the time, a form that was unique—a form that was human and yet not human. Close but no cigar. Homo erectushad yet to be discovered beyond the controversial material that Eugene DuBois had brought back from the Dutch East Indies (see post number 10 in this series) and the early discoveries of australopithecines in Africa were yet almost two to three decades away. Consequently, the specimen that Hauser found was the first concrete “human” fossil form that the scientific world had encountered and with which it had to grapple, even in the context of incomplete information.

The La Chapelle Neandertal was also an old man. This could be seen from the number of missing teeth and resorption of bone around those that had fallen out (Figure 2). Also present was considerable osteoarthritis, especially in the vertebrae. The arthritis may have caused some difficulty in walking and certainly would have been painful. It is, therefore, likely that this man walked in the manner of someone who would have had a cane (and may, in fact, have done so). Boule took this characteristic in the La Chapelle specimen and exaggerated it disproportionately, arguing that the Neandertal’s natural gait was slouching and primitive. Boule also focused on the sloping forehead and the huge eyes and nose, arguing that these were retrograde. He contended that these features strongly suggested a placement in the evolutionary line little above the great apes, with little to no intelligence that would have linked this race to modern humans (Boule, 1911-1913).

As Hammond (Hammond, 1982) points out, Boule’s description came around the time of the discovery of Piltdown Man. As we have seen, this find significantly influenced hominid evolutionary views for the next forty years. The clearly visible discrepancies between the morphology of Piltdown, which was thought to represent the dawn of humanity, and the La Chapelle Neandertal pushed this group out of the direct ancestry of modern humans onto a side branch. It was not until the exposure of Piltdown as a hoax in the early 1950s that the position of Neandertals was reexamined, since, candidly, there was no one else around that could serve as a proxy for our ancestors.

From this point on, the view of Neandertals began to change as the view of evolution as a theory changed. With the growth of the Evolutionary Species Concept, in which it was thought that one species could slowly, over time, transform to another, the view that Neanderthals might represent a phase of evolution toward modern humans gained ground. It was not until the development of systematics as a biological discipline in the 1980s and 1990s that the pendulum began to swing the other way again.

The Origin of the Neandertals

The best evidence that we have is that the Neandertals lived in an area that stretched from the western coast of Europe to as far east as southern Siberia (Figure 3). Their chronological origins suggest that they appeared on the scene between 200 and 300 thousand years ago. From descriptions of the fossil material found at the Sima de los Huesos cave at Atapuerca and other early archaic Homo sapiens sites, it is clear that there are incipient Neandertal traits in this population in the form of the massive faces, long heads and large brow ridges. This morphology is also present in the Petralona skull from Greece and represents, to an extent, a pan-European late archaic Homo sapiens. The complete suite of Neandertal characteristics did not coalesce, however, until around 100-120 thousand years ago.

Figure 3: Distribution of Significant Neandertal Finds in Europe and SW Asia (Adapted from Harvati, 2007)

Figure 3: Distribution of Significant Neandertal Finds in Europe and SW Asia (Adapted from Harvati, 2007)

Subsequent to the discoveries in Gibraltar, Engis, and Dusseldorf came rapid discoveries in the late 1800s and early 1900s, at Spy, in Belgium and the aforementioned La Chapelle Aux-Saints, La Ferrassie, and Le Moustier in the Dordogne Valley, in France.

Europe During the Early and Late Würm Glacial Periods

The Neandertals reached the height of their culture during one of the coldest time periods in history: the Würm glaciation. This stage in the earth’s history began roughly 120,000 years ago and ended just before 10,000 years ago. It is split into the Early and Late Würm with an interglacial period between 34 and 37 thousand years B.P. During the height of each glacial period, vast ice sheets covered the northern part of Europe, completely obscuring the British Isles, Scandinavia, the North Sea, northern Germany and the Russian steppes. During this time, the tundra line, which is normally associated with the beginning of arctic conditions, was located at what is modern-day Vienna. To say that these hominins survived and adapted in challenging conditions would be an understatement.

Changes From Early Archaic Homo sapiens:

Several distinct evolutionary adaptations are present in Neandertals compared to their precursors. There is an increase in the size of the head, such that, by the time of the classic Neandertals of Western Europe, brain size averages 1550 cubic centimeters, up from the early archaic Homo sapiens average of 1225 ccs. What is also notable about this is that it is approximately 100 ccs larger than that of modern humans. This particular trait is still poorly understood but may be a by-product of the systemic adaptations to the cold weather.

Another change is evident in the cranial expansion and reorganization that is exemplified by a view from the rear of the vault. In Homo erectusand early archaic Homo sapiens, the maximum breadth of the cranium was roughly at the level of the ears, but by the time of the Neandertals, it had moved up toward the middle of the vault. This gave the cranium a round shape, described by the French anthropologists of the early 20thcentury as “en bombe.”   Thus, while the maximum width of the vault did not change, the overall size of the brain did.  The angular torus, the ridge of bone extending from the ear to the back of the head, characteristic of Homo erectus, is now gone and the overall rear of the vault is more rounded with a pronounced “bun.”

In the front of the head, the brow ridges above the eyes, while being as large as those in Homo erectus, are now bifurcated, with a distinct depression above the nose. Further, from the early to the late Neandertals, there is a thinning of this ridge, suggesting a relaxation of selection pressures for its presence over time. The back teeth continue to get smaller, while the front teeth remain unchanged from the early archaics. Below the eyes, the infraorbital plates swing out, appearing as if someone had simply grabbed the nose and pulled. This is known as “midfacial prognathism.” Hypotheses have been proposed to explain this morphology, the most promising of which is that it is an adaptation to cold air. Given that the average daily temperature during much of the Early Würm was considerably lower than that of today, it has been suggested that, in order to bring the cold air up to blood-temperature levels, more space between the entrance to the nose and the brain would have been necessary. As the late Pleistocene wore on, Neandertal noses continued to increase in size.

As much as these cranial characteristics help to define Neandertals, however, there are striking changes in the post-cranium, as well. It is widely thought that these changes can at least partly be explained by two prevailing “rules” that govern body form in organisms. The first of these is Bergmann’s Rule, which posits that animal species will, over time, adapt, evolutionarily, to changes in temperature by either getting larger (cold weather) or smaller (warm weather). Just as a large piece of meat on a plate will take longer to cool down than a smaller piece, the purpose of increasing or decreasing size is to maximize or minimize heat retention.

The second rule is Allen’s Rule. This states that animals will maximize or minimize their surface area in response to heat or cold. For example, individuals of population groups in very cold areas tend to be shorter and stockier than those found in tropical locales. The less surface area that is exposed, the greater the ability to retain heat. The warmer the area, the longer the limbs tend to be. This allows more radiation of heat from the body.

The overall morphology of Neandertals conforms to these two rules, reflecting their adaptation to the extreme cold of Europe. In contrast to the early archaic Homo sapiens, the Neandertal trunk becomes shorter and the chest develops a “barrel” appearance. Additionally, the ends of the long bones (the humerus, radius, ulna, femur, and tibia) become shortened, as if someone had simply taken a chunk out of them toward the end. Neandertal height is also shorter than modern humans (males average 5 feet 4 inches and females 5 feet) and even late-surviving Homo erectus from Africa and Asia, and the long bones also have a characteristic bowing to them with very strong muscle markings. The overall appearance is one of compactness.

Important Neandertal Discoveries:

Beginning with the advent of Neandertal discoveries in the early 1800s, there has been a steady stream of finds to the present day. These can be broken down into three generally accepted periods: early, classic, and late.

Early Period Neandertals

The early Neandertals, which appear around 120,000 years ago, are represented by the fossils finds from Ehringsdorf in Germany, Saccopastore in Italy, and Krapina, in the Pannonian Basin of Central Europe three sites that are widely spread geographically. This suggests a selective advantage for this morphology and that there was major population radiation of it throughout Europe.

Figure 4: Saccopastore 1

Figure 4: Saccopastore 1

The best representative of this period is from the site of Saccopastore. Two crania from this site, near Rome, were discovered between 1929 and 1935. The date for these finds is uncertain but they are thought to be either from the Riss/Würm interglacial period or the early Würm, which would put them at between 120-125 thousand years B.P. (Spencer, 1997)

The Saccopastore 1 cranium (Figure 4) is mostly complete and displays very large brow ridges, a low, sloping forehead and a rounded back of the vault. This cranium shows the beginnings of the expanded midface, with large front teeth and nose that becomes prevalent in later Neandertals.

Classic Neandertals

Aside from the previously mentioned La Chapelle Neandertal, others of this time period come from the sites of Le Moustier, La Ferrassie, Gibraltar (Forbes Quarry), Monte Circeo (Guattari Cave), Spy and the hypodigm specimen from the site of Neandertal. All of the specimens from these site levels are thought to date from between 70 and 50 thousand years B.P.

Figure 5: The La Ferrassie 1 Neandertal

Figure 5: The La Ferrassie 1 Neandertal

Along with the La Chapelle Neandertal, perhaps the best example of this period is the complete adult cranium of La Ferrassie 1 (Figure 5). This was discovered in 1909 and is thought to be approximately 70 thousand years old. It has the characteristic occipital bun, flattening of the rear of the vault, sloping forehead, large brow ridges, and very large face. While these features are variable in other classic Neandertals, in La Ferrassie 1, they are all there to a significant degree.

Late Period Neandertals

The late period Neandertals date from between 50 thousand down to around 27 thousand years ago and much emphasis has been placed on them in drawing inferences as to the relationship between Neandertals and modern humans.  This group is represented principally by the Neandertal finds from the French sites of St. Cesaire, Arcy Sur-Cure, the Czech site of Vindija, and the Spanish site of Zafarraya. These Neandertals are characterized by a general reduction of traits that typify the classic Neandertals.

Figure 6: The Saint Cesaire Neandertal

Figure 6: The Saint Cesaire Neandertal

The best example of this group is from the site of St. Cesaire (Figure 6) in southwestern France, in the Charente-Maritimes district. Found in 1979, the find is thought to be between 40 and 41 thousand years old (Hublin et al., 2012). This Neandertal, while having some mid-facial prognathism has a generally flatter face and has a tooth-row that is reduced in size over the classic Neandertals. Additionally, while not prominent, there is a small chin, a characteristic that is present only in modern humans as a group. On the other hand, the brow ridges are very distinct, the forehead slopes back from glabella and the eye orbits and nose are quite large.

Of additional importance is the Zafarraya Neandertal, discovered in Northern Spain. The main find from this site is a mandible that exhibits classic Neandertal characteristics, having no chin, large front teeth in relation to back teeth, and a long dental arcade. The mandible is dated by Uranium/Thorium to slightly younger than 30,000 years B.P.

This is of critical importance because the earliest demonstrably modern humans in Europe are from the Moravian karst region of the Pannonian basin in central Europe, from the site of Mlade and date to the Early Würm/Late Würm interglacial—between 34 and 37 thousand years B.P. Other modern human finds from France and Germany have also been dated to between 30 and 32 thousand years B.P. This puts the Zafarraya Neandertal (and possibly St. Cesaire as well) in the overlap period with the earliest moderns. It has, consequently, been thought that these Neandertals represent very late-surviving refugia populations and they have figured into replacement models of modern human origins. These will be addressed in the next post.

Neandertal Tool Technology

Figure 7: Levallois Tool-Making Technique

Figure 7: Levallois Tool-Making Technique

As time wore on, the stone tool technologies of archaic Homo sapiens began to expand and they began to innovate from the basic hand axe template. While the hand axe was the hallmark of Homo erectus, archaic Homo sapiens began to experiment with scrapers. The critical cognitive shift was the move away from “core” tools to “flake” tools—using the core as a basis for the stone tool, not the tool itself. To this end, they invented, and perfected a stone tool creation method known as the Levallois technique (Figure 7). This was truly ingenious. First, a large, relatively flat core was found [1]. Then the sides were punched out [2]. Once this was done, the modified core was turned on its side and flakes were knocked off [3]. Then large flakes were removed in a sideways fashion [5 and 6]. This could be done in assembly-line fashion and produced two kinds of tools, the larger tools shown in [6] and the smaller, blade-like tools that were punched out. It is not entirely clear where or from what this stone tool technology evolved, although most view it as a radical re-envisioning of the blank used to make hand axes.

Figure 8: Neandertal-Made Bone Lissoirs

Figure 8: Neandertal-Made Bone Lissoirs

Recently, it has been discovered that Neandertals also created bone tools.  Working at the site of Pech-de-l’aze, research teams from the Max Planck Institute have discovered what they interpret to be lissoirs, or leather-working tools (Figure 8). The making of bone tools has been, up to now, associated with only anatomically modern Homo sapiens and this discovery suggests that Neandertals were capable of a wide range of tool-making behavior, despite the inhospitable conditions. Further, these researchers suggest that these tools may have originated with Neandertals. Marie Soressi, of Leiden University is quoted as saying:

“If Neandertals developed this type of bone tool on their own, it is possible that modern humans then acquired this technology from Neandertals. Modern humans seem to have entered Europe with pointed bone tools only, and soon after started to make lissoirs. This is the first possible evidence for transmission from Neandertals to our direct ancestors.”

Neandertal Burials and Social Behavior:

Another aspect of Neandertal existence that sheds some light on their situation is the considerable evidence that they buried their dead in ways that suggested an understanding, not just of death, but perhaps the significance of what death meant and how important life was. These burials have been found, principally, at La Chapelle, and La Ferrassie in Europe, Kebara, in the Levant, and Shanidar Cave, in Iraq, of which the discoverer, Ralph Solecki remarked “…although the body was archaic, the spirit was modern” (Solecki, 1971). They consist primarily of capstones, bodies placed in flexed positions, and bodies placed with flower arrangements (Leroi-Gourhan, 1975; Smirnov, 1989). Further, as is evident from the site of Dederiyeh Cave, in Syria and Teshik-Tash in Russia, infants were treated with extreme care and given their own burials (Dodo, Kondo, Muhesen, & Akazawa, 2002).

Another example of behavior that we typically only associate with modern humans is care for the infirm. At the Neandertal site of Shanidar Cave, in Iraq, several individuals suffered what were clearly injuries that would have led to that person having limited motor and mobility capabilities. Trinkaus and Zimmerman write:

However, these considerations also imply that the Neandertals had achieved a level of societal development in which disabled individuals were well cared for by other members of the social group. All of these individuals show extensive healing of their injuries, usually with little or no evidence of infection. Several of them, particularly Shanidar 1 and 3, lived for many years with severe disabling conditions, which would have prevented them from actively contributing to the subsistence of the local group. (Trinkaus & Zimmerman, 1982)

What comes next is the most contentious section in all of palaeoanthropology—the origins of modern humans. As we saw from Boule’s example, this is a study that is fraught with high emotion and strong opinions. As Christians, however, we have an added stake in the matter. Before us is the thorny question of whether or not these Neandertals, in any way, gave rise to us. If they did to any significant degree, then it perhaps forces us to consider how closely our genetic history is tied to questions about human uniqueness and the image of God.

Furthermore, as we inch toward our own species, it is becoming increasingly clear that these Neandertal precursors acted, in many ways, like us, and were it not for the crushing weight of the glacial conditions, might have excelled in more ways than what we see. This perhaps forces us to consider whether aspects of human culture are all that unique as well.

#The Origin of Modern Humans

The origin of modern humans is, perhaps, the thorniest area of palaeoanthropological research in existence. Much of this has to do, obviously, with the fact that it is we who are the subject of this research. As humans, we are taught at an early age that we are special, privileged, and important. Further, in conservative Christian thought, we are taught that we are God’s special creation, the products of his labors on the sixth day and the direct descendants of an original pair of humans, Adam and Eve. Throughout the Bible, we learn of this special relationship and how God desires us to be his people.

As a result of these perspectives, Christians have struggled with the science of human origins more so than other disciplines. To reinforce our uniqueness, it has become common among evangelical Christians to distance “us” from those that are not quite “us.” The issue of human origins has gained considerable traction in Christian circles, even reaching the pages of Christianity Today. The major scientific issue at hand is whether we as modern humans can be directly connected to the hominins we encounter in the fossil record that conventional palaeoanthropology identifies as archaic Homo sapiens.

As we have traveled through prehistory with this series, encountering hominins with varying degrees of cultural capacity and morphological “humanness,” we find that the difficulty with which we reject those that came before us as being ancestral to us becomes more acute as we near our own time. Put simply, the closer we get to modern humans, the more like “us” the fossils, and their associated trappings, become.

As we discovered in our examination of the Neandertals and other late archaic Homo sapiens, brain size was nearly the same, if not larger than our own, stone tool technologies were very advanced, approximating, as we shall see, those associated with modern humans, and behavioural customs became more recognizably human. But where, exactly, did we come from? Is there evidence for the earliest modern humans in the Holy Land? Is there a sharp break between those that preceded us, and us? Was there a time when there were only two humans on the planet?

The evidence for the origins of modern humans falls into three distinct categories: palaeoanthropological, archaeological, and genetic. Each of these will be dealt with separately and then assessed jointly—the post you’re reading, in three parts, will look at the paleoanthropological evidence from around the world.

Palaeoanthropology: The Fossil Record

It is important to understand that, with regard to the fossil record concerning the origins of modern humans, the scope of the information is enormous. As with most of this self-same record, though, completeness of individual specimens is lacking. A site may have hundreds of small to large bone fragments comprising the partial remains of many individuals but few to no complete specimens. It is from complete specimens (or at least complete crania) that we gain our greatest knowledge of comparative anatomy. As an example, the fact that the Zhoukoudian Homo erectus remains were so important was not because there were hundreds of bone fragments representing 40 individuals but because, when reconstructed, there were eight complete skull caps and associated faces which yielded considerable data regarding morphological diversity within that population. Thus, while evidence concerning the origins of modern humans is spread out over several hundred sites in the Old World, this review will only cover the most complete specimens.

Africa

Omo 1

Figure 1: Omo 1

Figure 1: Omo 1

The earliest fossil to be attributed to anatomically modern Homo sapiens anywhere is the Omo 1 skull, excavated in 1967 at the Omo Kibish site in southern Ethiopia, north of Lake Turkana. Originally dated to between 120 and 130 thousand years before the present (ky BP) by uranium/thorium dating, this skull has been recently been re-dated to 195 ky BP by argon/argon dating (McDougall, Brown, & Fleagle, 2005). While this date has largely been accepted as being reliable, visual observation of the fossil in question (Figure 1) suggests that some guesswork has gone into actually determining its morphology. While the rear of the vault is clearly rounded, like that of modern humans and what is preserved of the brow ridges are reduced, very little of the face has been preserved. Nonetheless, the weight of the evidence suggests that it is more modern than not.

Herto

Figure 2: BOU-VP-16/1

Figure 2: BOU-VP-16/1

The Herto remains from the site of Bouri, located in the Afar triangle in northern Ethiopia, also provide evidence of “post archaic” humans. These remains consist of two adults and one child and have been dated to 164 ky BP by Argon/Argon dating (White et al., 2003). These individuals are, on balance, modern human in morphology but with some archaic traits (Figure 2). The brow ridges remain large and projecting, while the back of the head protrudes, creating a flattened cranial base. On the modern side, the cranial capacity is large, the cranial walls are straighter and more house-shaped than those found in archaic Homo sapiens and the face is orthognathic, or pulled in, rather than the prognathic condition found in archaicHomo sapiensand especially Neandertals. Recall in Neandertals, the facial morphology appears as if someone grabbed the nose and pulled outward. The orthognathic condition is that found in modern humans.

Klasies River Mouth

This is a cave that looks out onto the Indian Ocean, at the tip of South Africa, near Humansdorp, in the Province of Eastern Cape. This site has three levels, one of which contained human remains dated to between 80 and 100 ky BP. The remains consist of five mandibles and assorted cranial fragments. Two of the mandibles have well-developed chins and one of the cranial fragments, a part of the frontal bone, just above the eyes, has a brow ridge that is modern in shape. On the strength of this information, the overall morphology of the sample is deemed modern.

Jebel Irhoud

Figure 3: Jebel Irhoud 1

Figure 3: Jebel Irhoud 1

The Moroccan site of Jebel Irhoud, in the southwest section of the Atlas Mountains, yielded two nearly complete adult crania and one juvenile mandible, dated to around 160 ky BP. While the cranial characteristics of the adult (Figure 3) are notably archaic, the face is quite modern in appearance, showing few to no archaic traits at all. Also importantly, examination of the juvenile mandible revealed a growth pattern only associated with modern humans. This pattern suggests an expanded childhood and development, at a time when most of our learned behavior is disseminated.

Taken in total, the African remains suggest a transition from archaic Homo sapiens to modern Homo sapiens that took place over the course of approximately 100 thousand years and involved different areas of the head and face. As we shall see, this pattern remains constant throughout the Old World remains that document this transition. The timing also has importance for the relationship between these modern humans and archaic Homo sapiens throughout the Old World. At a point where Neandertals, the last great phase of archaic Homo sapiens, were just coming into their own in Europe, the modern human form was gradually emerging in super- and sub-Saharan Africa.

Southwest Asia

Figure 4: Skhul V

Figure 4: Skhul V

Perhaps the most important early modern human fossils to be found outside of Africa come from the Holy Land, from the Israeli sites of Mugharet es-Skhul and Jebel Qafzeh, in the Mount Carmel region. Mugharet es-Skhul was excavated in the early 1930s and consists of approximately ten individuals, both adult and juvenile (Garrod, Bate, McCown, & Keith, 1939). Three skulls (IV, V and IX) from Skhul are complete enough to study and show a mixed pattern of relationships. Electron Paramagnetic Resonance dates of between 100 and 110 thousand years before the present (ky BP) have been established for the habitation layers at this site.

 

Figure 5: Skhul IV

Figure 5: Skhul IV

These hominins are extraordinarily variable in appearance. Skhul V (Figure 4), the most complete of the three is the most modern, with a high forehead and short vault. When compared, statistically, to a known modern human sample of over 2300 individuals (hereafter “modern human sample”) this skull is within the modern human range (Kidder, Jantz, & Smith, 1992). Such is not the case with Skhul IV (Figure 5) and IX, which exhibit very long and low vaults with faces that are pulled out. Visual and metric analysis of these skulls suggests, however, that they are not Neandertal in appearance but are, rather, more similar to the early moderns from North Africa and, thus may represent a general pan-North African/Levantine population or a migrant population of incipient moderns. About the remains from this site, the excavators wrote this:

We are of the opinion that the variability found amongst the fossil people o f Mount Carmel is greater in degree and in kind than is to be observed in any local community of modern times. Had the Mount Carmel people been discovered—not collectively, in one place, but separately, in diverse localities, each excavator would have been convinced that a new and separate form of humanity had been unearthed, so great does one Carmelite individual differ from another. (McCown & Keith, 1939)

Not far from the site of Skhul is the site of Jebel Qafzeh, yielding the other large cache of modern human remains from the region. This site was excavated between 1932 and 1935 and yielded a number of remains including two complete crania, Qafzeh 6 and 9. Smith (pers. comm.) has indicated that skull 9 is likely intrusive while 6 is contemporaneous with the deposits. This skull has been dated by Thermoluminescence and Electron Spin Resonance to between 92 and 101 ky BP. Qafzeh 6 is regarded by most researchers as modern human although we noted some archaic characteristics for it. For one, the skull is long and very wide compared to the modern human sample (Kidder et al., 1992). When included with the Skhul remains, it is clear that a population that was on the cusp of modernity was resident in this area.

The Levant also contains three sites that yielded Neandertal remains, Mugharet es-Tabun, Amud, and Kebara. Of these, the Tabun and Amud sites yielded relatively complete skulls and their morphology differs from the classic Neandertals of Europe insignificantly. When the modern human remains are compared to the Neandertal remains in the area, chronologically, however, a confusing pattern emerges. The best dates for the Neandertals are between 50 and 70 ky BP, which places them after the modern humans in the area. Of additional consternation is that, as discussed above, the archaic traits do not indicate a Neandertal pattern. This seems to suggest that the Neandertals existed in this region to the exclusion of the modern humans.

Also oddly, subsequent to the Skhul/Qafzeh sample, there are no modern human remains in this region until approximately 40 000 years BP, a gap that is explained by Shea and Bar-Yosef as reflecting a failure of the Skhul/Qafzeh moderns to gain a foothold in the region (Shea & Bar-Yosef, 2005). This model effectively argues that, counter to modern sensibilities, the Levantine Neandertals outcompeted the early moderns in the area and drove them out.

Europe

It is tempting to regard Europe as an evolutionary backwater in the pantheon of human evolution simply because few (if any) major evolutionary changes originated there.  Rather, it just seemed like “a good place to relocate.”  While it is true that Neandertals developed their peculiar morphology here, other evolutionary trajectories, especially those involving the populations represented by the slightly earlier Sima de Los Huesos remains are murky.  Although several genetic studies have suggested that there was a split between Neandertals and other archaic groups around 400 thousand years ago, it is anybody’s guess where that occurred, especially given that Neandertal morphology did not appear until between 200 and 300 thousand years ago.

The other primary reason that Europe is regarded as a backwater is that, where modern humans are concerned, the pace of evolution has lagged behind that of Africa and the Near East and the earliest known anatomically modern humans from the region date to no more than 34 to 37 ky BP, some 100 to 160 thousand years after the first appearance of moderns in Africa. The frustration among European palaeoanthropologists resulting from these issues has persisted since the middle-1800s and is, in part, responsible for the Piltdown debacle (See The Lack of Acceptance of Australopithecus and the Piltdown Forgery in this post). While it is quite possible that the whole Piltdown hoax was conceived of as an elaborate prank, that European paleontologists were so willing to claim the purported first modern human as their own clouded the judgments of some, otherwise very thoughtful and professional, minds.

Despite these shortcomings, the amount of effort that has been placed on European palaeoanthropology in the last 200 years has resulted in a wealth of hominin material relating to the appearance of modern humans that is unparalleled in the rest of the Old World, so much so that it would be impossible to describe even half of the most important finds in this review. I will focus, instead on a few sites that provide critical information regarding the trajectory of modern human evolution in this area.

Mlade?

Figure 6: Mlade? 5

Figure 6: Mlade? 5

The first modern Europeans appear in the Moravian Karst region of the Czech Republic, at the site of Mlade?. These were excavated in 1925 and, because of the complex cave stratigraphy, have been dated biostratigraphically to before 32 thousand years ago but before 40 thousand (Wolpoff, 2011). Conventional thought is that the skulls date to between 34 and 37 thousand years ago (Laville, 1988). This coincides with the Early Würm/Late Würm interglacial period and they represent, perhaps, one of the first populations to expand into (the now slightly more hospitable) Europe. The fossil material from this site is comprised of six partial to complete skulls and other fragments. While these fossils have been characterized as generally modern, they have been used as evidence by those espousing versions of regional continuity between Neandertals and early moderns in the region based on the presence of archaic traits. For example, while Mlade? 1 and 6 are quite modern-looking, Mlade? 5 (Figure 6) has a very long, low cranium with significant “bunning” at the back of the skull and, from the rear of the vault, is as wide at the base as it is near the top. However, the brow ridges are small and what is preserved of the face (not shown) is modern.

Cro-Magnon

Figure 7: Cro Magnon 1

Figure 7: Cro Magnon 1

Perhaps the most well-known site in Europe is the site of Cro-Magnon, located in the Dordogne region of France. Excavated in 1868 while a railway was being constructed, the remains from the site, which consist of two complete crania, CM 1 and 2 and the top of a head, CM 3, along with some arm and leg bone fragments, have been dated only biostratigraphically as being slightly less than 30 thousand years old. Cro-Magnon 1 (Figure 7) exhibits modern cranial curvature and possesses a very high forehead but comparison to a sample of known modern humans reveals that cranial lengths and widths are still expanded over the modern condition. The brow ridges, on the other hand, are small, and all of the associated mandibles have large chins. The skulls are short, high and house-shaped from the rear (Pruner-Bey, Lartet, & Christy, 1875).

Vogelherd

Dated to approximately the same time period is the Vogelherd site, which yielded only three individuals, one of which was an almost complete skull that is missing the face. The other two remains consist of a partial skull and a humerus. Very little of the Vogelherd 1 cranium is archaic in nature and the skull has a very high forehead, small brow ridges and is quite gracile in appearance. Only the slight protuberance at the back of the head and a slight roundness to the vault suggest an archaic past.

East Asia

The fossil record for early modern humans is considerably more fragmentary in East Asia than in Africa or the Near East. While there is a documented transition in China between the late Homo erectus population at Zhoukoudian to the archaic Homo sapiens remains of Dali and Mapa (described in the last post in this series), there is little in the way of transitional forms from the latter to modern humans. Subsequent to the appearance of these crania, the next hominins that factor into the origins of modern humans in East Asia are the Liujiang and Zhiren Cave fossils.

Liujiang

Figure 8: Liujiang

Figure 8: Liujiang

The Liujiang cave specimen was discovered in 1958 in the province of Guangxi Zhuang, in Southwest China and is an almost perfectly preserved cranium along with some scattered postcranial fragments. Recent Uranium Series dates for this cranium have been obtained (Shen et al., 2002) that place this hominin between 111 and 139 thousand years B.P. Brown (Brown, 1999) describes this specimen (Figure 8) as having a “long and low cranial vault, with an occipital bun…” although it is visually difficult to corroborate this. The face is small and clearly modern and, when compared to a large sample of modern humans, the skull did not fall outside the 95% confidence boundary of the modern human sample (Kidder et al., 1992). Therefore, if the U-series date can be believed, a completely modern human morphology was in place in southern China by at least 100 thousand years B.P.

Zhiren Cave

Figure 9: Zhiren Cave Mandible

Figure 9: Zhiren Cave Mandible

Also located in the Guangxi Zhuang area, Zhiren Cave yielded several teeth and a large section of a human mandible. Using extinct animal correlations and uranium series dating, the remains are thought to be between 100 and 106 thousand years old (Figure 9). The remains are distinctive in that a clear chin is present on the mandible. This is a trait that is only found on modern humans. If the date holds up (and at this point, there is no reason to suspect otherwise) then it would signal a migration of modern humans out of Africa sometime between 100 and 150 thousand years ago.

Three other East Asian sites with skeletal remains, although dated very late, are worth mentioning: Zhoukoudian Upper Cave, Tianyuan Cave, and the Japanese Minatogawa site. While the Tianyuan Cave has produced only postcranial fossils, the associated date by AMS Radiocarbon is between 35 and 33 thousand years B.P. As Kaifu and Fujita (Kaifu & Fujita, 2012) note, these remains are indistinguishable from modern populations and denote the appearance of clearly modern humans in this area by 40 thousand years B.P. One of the problems unique to the Japanese archipelago is that, due to the acidity of the soil, no human remains of any kind have been found dated prior to this.

Figure 10: Upper Cave 101

Figure 10: Upper Cave 101

The Zhoukoudian Upper Cave remains consist of three complete crania (101-103), and some mandibular and postcranial fragments. Unfortunately, like the Zhoukoudian Homo erectus remains, they were lost during the run-up to World War II and only casts survive. Equally distressing is that skull number 102 was crushed post-mortem and no attempt was made to reconstruct it before it was cast, so no usable measurements can be taken from it. The other two crania show a confusing pattern of relatedness to other regional populations and studies have variously pegged them as Southeast Asian, European, African and Native American in morphology. Further adding to the confusion is that the date for the remains cannot be bracketed any more tightly than 12 to 30 thousand years B.P. Consequently, for all intents and purposes, it looks like they simply dropped out of the sky. Our research indicated that the 101 cranium (Figure 10) fell within the range of the modern human sample but only if size was controlled (Kidder et al., 1992). The cranium is larger than most modern humans but proportionally so.

The Minatogawa remains, from the Island of Okinawa, are more securely dated to around 24 thousand years B.P. (Baba, Narasaki, & Ohyama, 1998) and are thought to have their origin in Southeast Asia. These remains consist of an almost complete skeleton and three partial skeletons that are demonstrably modern in appearance.

It is difficult to draw evolutionary patterns in this region other to state that it appears that modern humans were there by around 100 thousand years ago. When they got there is currently unknown. It is further, nigh impossible to compare the scope and trajectory of the change from archaic Homo sapiens to modern Homo sapiens here. Liujiang has very few archaic traits and the Zhiren Cave remains are simply too fragmentary to draw comprehensive conclusions of any kind.

Pope (Pope, 1992) has argued that some characteristics that are present in the Liujiang cranium, such as a flattened frontal bone, rectangular eye orbits and a flat midface can be found on the Dali specimen, but also admits that, given the modernity of the find, the early date is “remarkable.” Regarding Zhiren Cave, while Liu and colleagues (Liu et al., 2010) have described the mandible as modern, they note that, overall, it is large and robust and mayprovide a link to populations that came before. At this point, however, given the information we have for this region, we simply do not know.

Australasia

Figure 11: Willandra Lakes Hominid 50

Figure 11: Willandra Lakes Hominid 50

The earliest securely dated remains in Australasia are from the Australian sites of Lake Mungo and Willandra Lakes. Lake Mungo yielded the remains of several individuals, all of which are thought to be around 57-62 thousand years B.P (Thorne et al., 1999). Lake Mungo 3 is an almost complete, flexed burial with morphological characteristics that are very gracile with no archaic characteristics whatever (Bowler & Thorne, 1976).

The Willandra Lakes Hominid 50 specimen (Figure 11) was discovered as a burial in New South Wales in 1980 and is bracketed between 12.2 and 32.8 ky B.P., younger than the Lake Mungo burial (Grün et al., 2011). The mostly complete vault is very long and robust, with a low forehead and a prominent brow ridge. The morphology of this skull has led Hawks et al. (Hawks et al., 2000) and to argue that it has direct links to the Ngandong fossils and represents continuity from archaicHomo sapiens to modern Homo sapiens in this region.

Arguing against this perspective, of course, is that the Lake Mungo cranium is earlier and much more modern. It, therefore, has been suggested that there were independent migrations into this area represented by each of these populations. This is, however, equally problematic since the Lake Mungo locality is within the Willandra Lakes region and the two sites are very close together. Given the recently discovered variability in the synchronic Dmanisi remains, it therefore seems reasonable to argue that the two different specimens represent morphologically variable diachronic populations in the area. Whether they are, then, the direct descendants of the Ngandong population is not known.

Conclusion

The appearance of the modern human form is, based on these data, staggered in timing and is, perhaps, partially topographically dependent. While it seems that modern humanity gets its beginnings in North Africa, there is rapid migration out to both the Near East and the Far East. What is not clear is the relationship between the archaic Homo sapiens populations and the moderns. We know, based on the genetic evidence that will be examined in a future post, that there was mixing with the locals such that Neandertal genes exist to this day in European populations. How much mixing is still unclear, however. Further, as we shall see, there was as yet another genetically distinct population from the Neandertals and early moderns, represented by a single finger bone found in Denisova Cave, in the Steppes of Eurasia, northeast of Kazakhstan. Do these three groups represent a highly polytypic species that interbred at the peripheries of their ranges? Do they represent a syngameon, different species that interbred at the peripheries only when necessary? These questions are still being debated in palaeoanthropological circles.

One thing is clear from this survey, however: the earliest sites with modern human remains have been securely dated to greater than 150,000 years ago. While young earth creationists have attempted to denigrate and dismiss modern radiometric methods, such attempts have been without success. These methods are extremely robust and very well understood.

As importantly, however, no early modern human remains have been discovered in the Fertile Crescent, the area where it is presumed that the activities recorded in the early chapters of Genesis took place. In fact, this region has yielded no concrete human remains prior to the Neolithic period, some 8,000 to 10,000 years ago.

These two points have profound implications for the traditional understanding of the Garden of Eden account. The appearance of modern humans at this early date exceeds any literal reconstruction of the biblical texts in Genesis involving the appearance of Adam and Eve. Further, the placement of these earliest moderns strongly suggests that they cannot be incorporated into any version of the events of Genesis 2-4 as traditionally understood. They seem to be completely extraneous to the story. If this is the case, how are we to interpret these chapters?

Were Adam and Eve, as some have suggested, Neolithic farmers, being only two of many people alive at the time? Is the story of Adam and Eve symbolic, representative only of humans as a whole? While the palaeontological evidence alone is not sufficient to answer these questions conclusively, these data strongly suggest that while either of these options is viable, a straight, literal reading of the text is not.


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James Kidder
About the Author

James Kidder

James Kidder holds a Ph.D. in Biological Anthropology from the University of Tennessee (UT). He currently employed as an instructor at UT, and as a science research librarian at Oak Ridge National Laboratory. He has been involved in the Veritas Forum at UT and runs the blog "Science and Religion: A View from an Evolutionary Creationist/Theistic Evolutionist."


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