Four years ago, I wrote about the "Dragon Man" fossil skull found in the Dragon River region of northeastern China. This week new studies of this skull have been published in Cell (Qiaomei Fu et al. 2025) and Science (Qiaomei Fu et al. 2025b) showing that the DNA in this fossilized skull identifies it as one of the Denisovans, a group of humans that split from the Neanderthal line and survived for hundreds of thousands of years before going extinct. Carl Zimmer (2025) has written a good article on this research.
Denisovan fossils were first discovered in 2010 in the Denisova Cave in Siberia. Since then, other Denisovan fossils have been found in a high-altitude cave in Tibet, in a cave in Laos, and in both the highlands and lowlands of New Guinea, which indicates that these people were flexible enough to live in a wide range of environments.
Billions of people today carry Denisovan DNA, inherited from human interbreeding with Denisovans hundreds of thousands of years ago.
Until now the Denisovan fossils have been a few small fragments--half a broken jaw, a finger bone, a small fragment of a skull, three loose teeth, and four chips of bone. But now the identification of the Dragon Man skull as Denisovan allows us for the first time to see what a Denisovan face looked like.
The Dragon Man skull's cranial capacity is around 1,420 cubic centimeters, which puts it within the range of modern humans. But there are some differences in the fossil skulls that point to ways that Homo sapiens surpasses other Homo species. One of the most evident differences is in the brow ridges. Notice how far the brow ridge of Dragon Man projects from the face, much farther out than for a typical Homo sapiens skull. A similar difference can be seen even within the evolutionary history of Homo sapiens. The older human skulls show a more prominent brow ridge than the younger human skulls. Men tend to have thicker, more overhanging brow ridges than women, which is caused by men having higher levels of testosterone than women during their development, particularly during puberty. So we can say that the skulls of Homo sapiens are more "feminized" than the skulls of other Homo species like Dragon Man, just as younger human skulls are more "feminized" than older human skulls. You can see this craniofacial feminization in these human skulls:
On the left, you see a 110,000 to 90,000 years-old human male in lateral (top) and frontal (bottom) views, compared to that of a recent African male (right). The older skull on the left shows the large brow ridges and long and narrow, masculinized face characteristic of Middle Stone Age/Middle Paleolithic-associated humans, as compared to the more feminized face of recent humans.
As I indicated in my previous post, this can be seen as evidence for the Human Self-Domestication Hypothesis: just as some wild animals have evolved through domestication to become tame animals living around human beings, so have human beings domesticated themselves in that ancient human ancestors were selected for being less aggressive and more socially tolerant individuals; and thus human beings have evolved by self-domestication through what Brian Hare has called "survival of the friendliest." Some of the evidence for this is found in our anatomy, particularly in our faces.
The neurotransmitters and hormones that mediate aggressiveness have effects on skeletal development, particularly in craniofacial growth and development. So if there has been evolutionary selection for social tolerance--for survival of the friendliest--we can expect to see changes in skeletal morphology, so that in human evolution younger human skulls are more "feminized" than older human skulls.
This could explain why Homo sapiens has survived to the present, while the other Homo species--like the Denisovans--have gone extinct. Through self-domestication, human ancestors were selected for being less aggressive and more socially cooperative individuals. Because of this increase in social tolerance, people in densely populated groups could cooperate with one another rather than fall into conflict. This would allow for increasing human populations with dense social networks, so that more people interacting with one another promoted the generation, retention, and diffusion of cultural innovations, which would stimulate complex symbolic and cultural behavior as indicated by language, art, ornamentation, hunting and fishing technology, music, and long-distance trade.
The Denisovans like Dragon Man failed to achieve this, and consequently they went extinct except for some of their DNA that survives today in Homo sapiens because of ancient interbreeding between the different hominid species.
REFERENCES
Qiaomei Fu et al. 2025a. "Denisovan Mitochondrial DNA from Dental Calculus of the >146,000-year-old Harbin Cranium." Cell 188: 1-8.
Qiaomei Fu et al. 2025b. "The Proteome of the Late Middle Pleistocene Harbin Individual." Science (June 19).
Zimmer, Carl. 2025. "Mysterious Ancient Humans Now Have a Face." The New York Times (June 18).
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