Fossils Found in China Come from a Huge Human Ancestor, Scientists Say

A pair of scientists who study hominin fossils and human evolution in China and East Asia claim to have discovered a new human ancestor that appeared during the Late Quaternary or Middle Pleistocene era, about 300,000 years ago. They have named this species Homo juluensis, which is in reference to the unusually large size of this theoretical addition to the official hominin roster ( ju lu means “huge head” in Chinese).

This discovery did not emerge as a result of any amazing new fossil finds. In fact, the fossils that the scientists say prove the existence of the new species were recovered in the 1970s at the Xujiayao archaeological site in China, which sits on the border between the provinces of Hebei and Shanxi in the northern part of the country. It was a fresh re-examination of these fossils that led to the discovery of the new species, although more research will be needed to prove to everyone’s satisfaction that Homo juluensis really did exist.

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Bone fragments from several individuals at the Xujiayao site in China are challenging long-held assumptions about the region’s fossil record. (Wu Xiujie/Nature)

Some Really Big Human Cousins

The fossilized remains of 16 individuals recovered from the site at Xujiayao, along with a large collection of stone tools and animal bones. These remains have been dated to between 200,000 and 160,000 years ago, during a glacial period when global temperatures were significantly colder on average than they are now.

In an article published in the journal Nature Communications, Christopher Bae, a professor of anthropology at the University of Hawaii at Manoa, and Xiujie Wu, a paleoanthropologist from the Chinese Academy of Sciences, present what they consider conclusive evidence that this 50-year-old fossil collection comes from a species of archaic human that they were the first to recognize.

During the Middle and Late Pleistocene eras, from about 300,000 to 50,000 years ago, there were a number of archaic human species living in Eurasia and in the lands of eastern Asia (China, Japan, Korea, and the southeast Asian countries) in particular. This intermingling has created some confusion for those attempting to interpret the fossil record correctly, Bae and Wu claim, but the two scientists say they created a new way to organize and analyze the fossil record that allowed them to make their shocking discovery.

“This study clarifies a hominin fossil record that has tended to exclude anything that cannot easily be assigned to Homo erectus, Homo neanderthalensis, or Homo sapiens,” Bae said in a University of Hawaii press release.

“Although we started this project several years ago, we did not expect being able to propose a new hominin (human ancestor) species and then to be able to organize the hominin fossils from Asia into different groups. Ultimately, this should help with science communication.”

Homo juluensis (blue five-pointed stars) includes Xujiayao, Xuchang, Xiahe, Penghu, Denisova, and Tam Ngu Hao 2; Homo longi (white triangles) includes Harbin, Dali, and Jinniushan; Homo floresiensis (pink diamond) includes Liang Bua; Homo luzonensis (green circle) includes Callao. Although elsewhere we had tentatively grouped Hualongdong (black inverted triangle) with the H. longi fossils we keep it separate for now pending further ongoing investigation. In many studies, Maba and Narmada (black squares) have been grouped together to form a separate population. It may be possible following further analyses that these latter fossils may be included in the broader H. neanderthalensis species or assigned a new taxonomic name altogether. The accompanying Box includes descriptive information for the type specimens and sites for the four hominin species discussed here: H. floresiensis; H. luzonensis; H. longi; H. juluensis. (Bae & Wu/Nature)

In looking more closely at these ancient specimens, what caught Bae’s and Wu’s attention as much as anything was their sheer size. The skulls of these hominins measured between 103 and 109 cubic inches (1,700 and 1,800 cubic centimeters) in volume, in contrast to ancient Homo sapiens skulls that averaged about 81 cubic inches (1,350 cubic centimeters) in volume. Even Neanderthals lagged well behind Homo juluensis, with an average skull volume of 88 cubic inches (1,450 cubic centimeters).

These were indeed big-headed creatures, and while Homo juluensis couldn’t be classified as a giant, its size still helps to set it clearly apart from modern humans.

“That is a very substantial difference between modern Homo sapiens, Neanderthals, and this new proposed species,” Bae said in an interview with the South China Morning Post.

“The eastern Asian record is prompting us to recognize just how complex human evolution is more generally and really forcing us to revise and rethink our interpretations of various evolutionary models to better match the growing fossil record.”

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The nine Xujiayao teeth fossils used in the study. (Bae & Wu/Nature)

Rethinking the Denisovans

One of the more stunning assertions made by Bae and Wu concerns their claim about the true origin of the Denisovans. These mysterious human ancestors were only added to the list of known archaic hominins in 2008, after a scattering of their fossils were recovered from the Denisovan Cave in the Altai Mountains of Siberia.

Like Homo juluensis, the Denisovans had unusual teeth, with their size and shape distinguishing them from Neanderthals and Homo sapiens. This puts them much closer to Homo juluensis than to the other two, and Bae and Wu believe this is highly significant.

“One of the things that always stood out about the Denisovan molars was that they were quite large. The molars from Xujiayao from our type specimen are also quite large,” Bae said, before going on to explain that he does not think this is a coincidence.

In comparing the biting surfaces of Denisovan teeth and those from the species found in Xujiayao, the Bae and Wu determined that they were “almost exactly the same.”

Based on this observation, and the anomalous presence of the Denisovans that took so long to detect, the researchers believe the Denisovans were actually a Homo juluensis population, and not a separate hominin species at all.

This theory is bound to generate controversy, since evolutionary scientists have widely accepted the Denisovans as a distinct human ancestor. If the existence of Homo juluensis is ultimately verified by other experts, however, it certainly could lead to a change in the Denisovans’ official status.

Homo Sapiens, Neanderthals, Homo Juluensis … Could There Be Others?

Through further study of the stone tools and animal bones found at the Xujiayao site, the researchers have been able to reconstruct the Homo juluensis lifestyle, at least at this one location.

They were highly dependent on wild horses, it appears, hunting and butchering them and consuming their meat, cartilage and bone marrow. They would have used the skins of the horses to make clothing to cover themselves, which would have helped them survive the extreme wintertime weather conditions they would have experienced during the glacial period they lived in. Because they had to survive in a harsh climate, Homo juluensis would have lived in small groups and maintained small population numbers overall, explaining why their fossils have not been discovered before.

Bae and Wu believe the species would have gone extinct approximately 120,000 years ago, following the earliest Homo sapiens migrations into the lands of modern-day China. But some of their DNA would have survived through interbreeding with humans, and if the scientists are right, that would explain why Denisovan DNA that has already been detected in the human genome.

“Recent research initiatives in China, and broader eastern Asia, are showing clearly that multiple hominin lineages were present during the Late Quaternary,” the researchers wrote in their Nature Communications article. Between 300,000 and 50,000 years ago this region was a beehive of hominin activity, raising the possibility that there might be another unknown hominin species or two still waiting to be discovered.

Top image: New organization of hominin fossils from eastern Asia after discovery of new species. Source: Bae & Wu/Nature

By Nathan Falde