The Human Fossil Record, Part 10a: Homo erectus in Asia
Note: Today and tomorrow, Dr. James Kidder continues to tell the story of the evolution of creatures on our own small branch of the primate family tree, the hominins. Kidder’s previous post in the series looked at fossil evidence helping anthropologists answer the question, “When did our ancestors first start exploring beyond the African continent?” and focused on sites in Europe and the Middle East. Here Kidder turns our attention east and describes the discovery Homo erectus.
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.
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:
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.
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.
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.
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.
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 of Homo erectus fossils ever found at one site, as well as presenting one of the greatest mysteries in paleoanthropology. Tomorrow, 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.