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The Human Fossil Record, Part 5: The Dispersal of the Australopithecines

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June 16, 2011 Tags: Human Origins

Today's entry was written by James Kidder. Please note the views expressed here are those of the author, not necessarily of BioLogos. You can read more about what we believe here.

As we learned in the previous post, up 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 of A. 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. Boisei is found down to approximately 1.2 million years ago.

In our next post we will look at the South African forms, as well as the extinction and importance of Australopithecus.

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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Pete D - #62729

June 19th 2011

Yes Roger, any book that begins with a super-being willing something into existence is obviously the bedrock of science. Particularly one that includes talking serpents and magical fruit. Although, I’m curious as to why you think that the notion of disobeying a supernatural entity is deserving of death and eternal damnation is such an important idea.

Pete D - #62734

June 20th 2011

@beaglelady - lol…no. Again, my point is how do you separate literal claims from metaphorical ones in the bible where it is not obvious from context? Does the understanding of god’s word require extensive knowledge of the anthropology of ancient cultures? If you classify Genesis as narrative myth because it is so obviously wrong (as shown by science) as a literal account, then why not the parting of the Red Sea or the Resurrection?

Jimpithecus - #62736

June 20th 2011

Pete, I think that one of the ways in which you do this is by identifying the context of the passage, the literary style of the passage and that these things give you the point of the passage.  Obviously, we are addressing some passages that are over 3000 years old and we might never know exactly why something was written. 

This is why I have basically sworn off “inductive Bible studies.”  They make a point of stripping the passage of any of its context.  This leads to very idiotic interpretations (see AiG, ICR).  All homiletics and no hermeneutics. 

beaglelady - #62751

June 20th 2011

By knowing something about different genres found in Scripture.

Pete D - #62753

June 20th 2011

So understanding god’s word requires sophisticated knowledge of literature, history, and anthropology. Or do the misled (like Baptists?) get a pass because of their lack of knowledge of ancient history?

beaglelady - #62756

June 20th 2011

Well, we need scholars with sophisticated knowledge of ancient languages to translate the Bible.  Or I do, anyway.  Got something against knowledge and education?

Pete D - #62770

June 21st 2011

Not at all. Education is the best remedy for superstition. My point is that it seems to be exceedingly difficult for the god of the bible to reveal his “truths” to the people he loves (particularly the poor, who have little or no access to education) without using thousands of words in different ways that mislead so many.

beaglelady - #62772

June 21st 2011

That’s why we have educated ministers (or why we should have educated ministers).  Even back in the terrible days of slavery in the U.S., Black ministers were allowed to get an education.  Their congregations were largely illiterate. Educating congregations is also the best way to keep people from being swayed by cults. 

Pete D - #62773

June 21st 2011

Well evidently there is a lot of confusion as to the proper education for ministers. Back in the day, Paul preached about Jesus saving humanity from the sin of a literal Adam. Now Adam is just a construct from a narrative myth meant to impart a deeper spiritual truth. How could the author of so much of the NT have been so misinformed? How much understanding of the times of Genesis did the Jews in the times of Moses have (even they believed in a literal 6 day creation)?

beaglelady - #62775

June 21st 2011

Paul believed in a 3-tier universe. Heaven was above us ,and hell  (an underworld) was below. So do we reject Paul, or do we embrace the 3-tier universe of his time?

Pete D - #62778

June 21st 2011

Well now you’re getting at it! The authors of God’s revealed truths seem be pretty bad at getting things right or communicating what they really mean. My point this whole time has been this…you cannot rely on revelation for truth. Time and again, the revealed “truths” of the bible have been shown false. There is no reason to lend any credibility to any of the fantastic claims found within it! Jericho’s walls blown down by trumpets and shouting. Ridiculous.

BTW - I reject both Paul and the 3-tiered universe.

beaglelady - #62780

June 21st 2011

And you are the source of revelation, obviously.  

Pete D - #62792

June 21st 2011

lol…don’t know where you find that in what I’ve written.

beaglelady - #62882

June 24th 2011

I misunderstood you; sorry.

Pete D - #62737

June 20th 2011

I understand the need to take that approach, Jim. This still does not overcome the problem of impossibilities explicitly stated as fact in later books of the bible - including the resurrection. What other interpretation can one give to Moses parting the Rea Sea or Jesus rising from the dead?

Jimpithecus - #62741

June 20th 2011

Why is the resurrection an impossibility?

Pete D - #62744

June 20th 2011

Dead people cannot come back to life and walk around for 40 days with gaping abdominal wounds.

R Hampton - #62750

June 20th 2011

The key point being dead people, and not the eternal Jesus Christ of the Holy Trinity.

Pete D - #62752

June 20th 2011

The key point being that Genesis 1 cannot be taken literally because the scientific evidence overwhelmingly shows it is impossible…unless you’d like to claim that the eternally tricky God of the Holy Trinity made it look that way. Once you allow magic to make the impossible possible, the sky is the limit! Seas parting, the dead rising, demons making pigs drown, angels of death killing your firstborn, people living in whales bellies, etc. etc.

Jimpithecus - #62755

June 20th 2011

This is very reductionistic.  It assumes that what is observable is all there is.  We cannot know that.  We can use scientific methods to render theories about what we do observe but there is much we cannot know.  This is not to say I am betting against science in and ID sort of way, but rather that we don’t live in a closed box. 

Pete D - #62769

June 21st 2011

I have not claimed that the observable is all there is. I am comfortable with “I don’t know.” But I am not speculating about what could be based upon ancient myths and claiming that as truth. I also am not trying to contort the claims of ancient myths to fit modern facts. There may be things we cannot know, but it is interesting that many people in the past also claimed there are things we cannot know that we now do know (atoms, subatomic particles, quantum phenomena). It’s interesting to me that your god is claimed to have interacted with the world in certain ways that are observable. When some of those interactions are shown to not have happened or are impossible, you deny  or change the claimed nature of those interactions to preserve your belief in that god. I understand that belief is a powerful thing to people, which is why we need an objective way to evaluate beliefs and reject those that don’t pass muster.

Gregory - #62776

June 21st 2011

“This is not to say I am betting against science in and ID sort of way” - Jimpithecus

Worth noting for attitude’s sake.

KevinR - #62763

June 21st 2011

You seem to forget and minimize the MAGIC required to get the big bang[ nothing gets out of singularity from a thermodynamic point of view - it needs tremendous outside help, impossible to happen by itself] and it’s evolutionary consequences going….miracle upon miracle upon miracle.
Life on earth is dependent on the sun being just so far, just so big, just so old. The earth revolving just so fast, tilted just so many degrees, water being just so constructed at 104.5 degrees, the moon being just so big, fast etc. The temperature being just within the right range, the sun being located in just the right spiral arm at exactly the right distance away from the center of the galaxy, the nuclear/subatomic forces being just the right amount. the flatness of the universe being tuned to just the right amount. Stars cannot form by themselves, neither can planets and so  galaxies. Need I go on?

Pete D - #62768

June 21st 2011

No rational person suggests magic as a source of the Big Bang, so I haven’t minimized a thing. Do you know what variation in the distance to the sun do you think life on earth could tolerate? Do you know what variation in the age of the sun could life on earth tolerate? I can calculate the bond angles in a water molecule from first principles considering only the forces between atomic nuclei and electrons without worrying about miracles. Stars and planets form due to gravity working on gas and dust. Need I go on?

Jimpithecus - #62799

June 22nd 2011

Are you saying that the “tweaking” would have happened anyway?

Jimpithecus - #62790

June 21st 2011

I have always had problems with this argument because it is post hoc.  The only reason that we are able to determine the “tweaking” of the universe is because we are here to do it.   Additionally, think of a room full of two hundred people.  Now imagine how many different decisions that each person has made over their lives and how many different possibilities they encountered.   The odds that they would all show up in the same room at the same time are astronomically small.  Yet there they are. 

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