Human Evolution in China: New Fossils Shed Light on the Relationship Between Neandertals, Modern Humans and Denisovans
Working at the open-air site of Linjing, China, palaeoanthropologists discovered what would turn out to be one of the most exciting East Asian human fossil finds in recent memory.
The Site of Linjing, China
In 2007, working at the open-air site of Linjing, China, palaeoanthropologists discovered what would turn out to be one of the most exciting East Asian human fossil finds in recent memory.
Working over the course of the next decade, the scientists have been able to recover the partial remains of two adult skulls that, when pieced back together, yield characteristics that are so striking and unexpected that they could completely alter our understanding of modern human evolution.
When they began to study the skulls, one of the first things the researchers noticed is that one of the skulls, Xuchang 1, is monstrous, with a size estimated to be 1800 cubic centimeters. To put this into perspective, the average modern human skull is 1450 cubic centimeters. This is a 24% increase, and it makes Xuchang 1 one of the largest skulls ever discovered.
The layer in which these human remains were found is estimated to date from between 105 and 130 thousand years ago (dated by optically-stimulated luminescence) and the skulls are, like all from this time period, very long, with receding foreheads. What is new and exciting about them is that they present a mosaic of characteristics that link them to many different people groups.
The skulls have several modern human characteristics, such as thin brow ridges and small and weak muscle markings. When viewing them from behind, however, the widest thickness is at the base. This is in contrast to modern humans, whose heads are widest toward the top of the skull (you can feel this if you put your hands on either side of your head). This particular characteristic is very, very old, appearing in skulls that are dated to over 500 thousand years before the present.
In addition to these oddities, the skulls have two distinct characteristics that are found only in Eurasian Neanderthals. On the back of the skull, there is a continuous ridge of bone, with a large dimple just above it, called a suprainiac fossa, while the inner ear only has features found in Neandertals. The confluence of these traits place these fossils in a unique position in the pantheon of human evolution.
What does this mean and why is it important?
These two discoveries come at a time when many discoveries are helping us to refine our understanding of modern human origins. Here is what we think we know: Beginning around 1.8 million years ago, a hominin form called Homo erectus left Africa for points east, eventually settling in Indonesia and China. These early humans were characterized by having heads roughly ¾ the size of modern humans with very large brow ridges and with their widest point just above the ears. They were also the first humans to conquer fire and perfect hunting.
Then, at some point, between 300 and 500 thousand years ago, a population group migrated from North Africa into Europe and, eventually into East Asia. The European branch became the Neandertals, between 200 and 250 thousand years ago, and the East Asian group eventually became the Denisovans. The Denisovans then spread east and south, eventually mixing with other populations, some of which were the precursors of the Melanesians and native Australians. The bulk of the Neandertals hunkered down in Europe and tried to outlast the bitter cold of not one but two glaciations. Despite this, while often pilloried in cultural literature as being half-witted brutes, Neandertals were a very complex society, with advanced weaponry and hunting behavior, grave goods, habitation structures and who practiced ritual behavior. Some populations of Neandertals eventually expanded their range into Western Asia and steppic Russia and interbred with the Denisovans. Unfortunately, as a culture, we know next to nothing about the Denisovans.
Roughly 100 thousand years after this, there was yet another wave of migration, between 100 and 60 thousand years ago, of early modern humans from North Africa, who moved north and East mixing with both the Neandertals in Europe and, perhaps, Western Asia and the Denisovans in East Asia.
These two Chinese skulls stand at the crossroads of these population movements. While showing clear Neandertal characteristics, they also express modern traits, possibly reflecting mixing with the late, modern human arrivals represented by the recent modern human finds at Daoxian. Yet they also express a clear link to ancient East Asian populations. The implications of these skulls are stark: there has been widespread population mixing and regional continuity in Europe and Asia for at least 400 thousand years. Not only did the Neandertals feel enough cultural kinship to mate and have children with these East Asian people, the early modern humans coming out of Africa did, as well. As Chris Davis of China Daily News put it: “One big happy family.”
The Roots of Modern Behavior
These new finds begin to answer some important questions in our understanding of human evolution, and yet raise more. What was the culture of these individuals like? How did it differ from the practices of those that came before and the people that they met? We have evidence that behavior that approximates a modern way of life began at least 300 thousand years ago, demonstrated at the European site of Shöningen, in Germany. Here, what was discovered is that the ancestors of the Neandertals created advanced bone and stone implements, and engaged in complex hunting and social behaviors (such as division of labor) that were consistent with a high level of “planning depth.” Further, they appear to have lived in a society with a highly advanced communication system. If such behavior characterizes all middle to late Pleistocene groups, then our understanding of what it means to be human must certainly be extended back that far.
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Charles Foster | Inhabit the World