Tuesday, March 07, 2017

Another Human Species in China?

The Christian Science Monitor and other outlets are reporting on a new find from Xuchang, China, that seems to possess intermediate traits between archaic and modern Homo sapiens:
In an article published Friday in the journal Science, the researchers note that the skull fragments date to the Late Pleistocene epoch, a time marked by the expansion of H. sapiens and the extinction of other species in the genus Homo. During the early part of that epoch, Neanderthals roamed Europe and western Asia while humans began to journey out of Africa. But fossil records of human species in Eastern Asia from that time period are thin, muddying the picture of that era for a substantial region of the planet.

The skulls found in China were found to bear very close resemblances to those of Neanderthals, including a very similar inner ear bone and a prominent brow ridge. But the brow ridge was much less pronounced than one would expect from Neanderthals, with a considerably less dense cranium, as one might expect in an early H. sapiens. Researchers also found that the skulls were large by both modern and Neanderthal standards, with a whopping 1800 cubic centimeters of brain capacity.
So where do they fit in the grand scheme of things?
"The overall cranial shape, especially the wide cranial base, and low neurocranial vault, indicate a pattern of continuity with the earlier, Middle Pleistocene eastern Eurasian humans. Yet the presence of two distinctive Neanderthal features ... argue for populational interactions across Eurasia during the late Middle and early Late Pleistocene," said Dr. Trinkaus in a statement.
This kind of population mixing makes sense. We already know that modern humans and Neandertals interbred in Europe and that the geographic range of Neandertals stretched from Portugal to Teshik Tash, in Russia and Shanidar Cave, in Iraq.

The remains are dated to Marine Oxygen Isotope Stage 5d or 5e, making them between 105 and 125 ky in age.  Here is a description of the neurocranium from the paper:
The large Xuchang 1 neurocranium closely approximates the shapes of those of Middle Pleistocene humans, especially eastern Eurasians (Fig. 2 and fig. S17). The vault height is low, similar to those of the Neandertals and the higher Middle Pleistocene vaults, and the low vault height is reflected in a low temporal squamous portion (figs. S27 and S28). It is also produced by the very flat midsagittal parietal arc. In contrast, the maximum cranial breadth is the largest known in the later Pleistocene (fig. S15), and it is securely based on an undistorted posterior cranium. Moreover, the widest point is low, on the temporal bones (fig. S17), as in most earlier crania, rather than on the parietal bones, as among Neandertals and most modern humans. In addition, the one complete mastoid process is short and slopes inward (fig. S17), rather than being longer and more vertical, as in modern humans and some Neandertals. These features combine to provide the cranium with an occipital profile similar to those of earlier human crania, contrasting with the rounded profiles of Neandertals and the laterally vertical ones of modern humans.
There are a few things that are immediately interesting about this. First, this skull is YUGE.  1800 cc is monstrous.  The average cranial capacity of modern humans is around 1450 cc and that of Neandertals, around 1550 cc.  Second, the low, flat cranium with the widest point on the temporal bones (just above your ears) are traits of Homo erectus, not modern humans or Neandertals, suggesting strongly that there was some sort of continuity from this group through to modern humans in this region.  Neandertals simply don't have those traits.  Nonetheless, the cranium clearly shows some Neandertal traits in the ear and rear of the vault.  This continuity is characterized by the authors thus: "This morphological combination, and particularly the presence of a mosaic not known among early Late Pleistocene humans in the western Old World, suggests a complex interaction of directional paleobiological changes and intra- and interregional population dynamics."  As more information becomes available, we will have a better idea of how this find fits in the east Asian evolutionary picture.  This is exciting.  Up until this point, we have had very few finds in China that fall within this general time frame, most notably the Dali and Mapa remains.  I will have to rework my section on human origins for the BioLogos site for this region. 


  1. I've heard some people suggest that perhaps these are finally skulls of the elusive Denisovians. What do you think?

  2. Well, here's the thing. A lot of migrations seem to come out of Steppic Asia. The modern Chinese originate from that area as did all of the population groups that overthrew the Roman empire in the 400s and 500s. It makes perfectly good sense that migrations of been coming out of that region for a long time. Especially if human habitation in Siberia and in around Denisova has a long time depth.

  3. "Have been coming out of". Sometimes, dictation doesn't work quite as well if you think it's going to.