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A collection of human-like fossils from China has baffled researchers for years, resisting clear classification or understanding.
The cranial pieces, dental structures, mandibles, and additional relics excavated from various locations throughout the nation undoubtedly belong to archaic hominins — the official term for taxa within the human line — who inhabited regions between 300,000 and 100,000 years past. However, it has remained ambiguous as to which specific species these skeletal elements originated from or how they fit into the progressively intricate branches of our ancestral tree.
Christopher Bae, an anthropologist at the University of Hawaii at Manoa in Honolulu who spent considerable time in Beijing, joins a group of researchers reassessing enigmatic fossils using modern perspectives. Alongside his collaborator Wu Xiujie, a distinguished professor from the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, he suggests it might be appropriate to acknowledge a hitherto unrecognized ancient human relative. They have recommended establishing a novel scientific species.
The most remarkable feature of this newly discovered ancient human relative was an exceptionally large brain, one that surpasses even that of our species, Homo sapiens—the sole remaining member of the hominins.
The characteristic is evident in the suggested name for the species, as disclosed by Bae and Wu in an article from November featured in the scientific journal. Nature Communications : Homo juluensis, a nod to “ju lu,” which means huge head in Chinese.
Their skulls are indeed extremely large; the estimated brain volume is around 1,700 to 1,800 cubic centimeters," explained Bae, who additionally detailed Homo juluensis in his publication The Paleolithic Studies in East Asia published in September." "Our minimum capacity is around 1,350 cubic centimeters, typically we're at approximately 1,450 (cc)." "While it may not be significantly bigger, it is considerably stronger.
The proposition has ignited debate amongst paleoanthropologists, with several experts arguing over whether the proposed classification qualifies as a distinct new species.
However, if Bae and Wu’s analysis holds true, these fossils might provide the answer to one of human evolution’s greatest enigmas—the mystery initiated by the finding of a little pinky bone within Denisova Cave situated in the Altai Mountains of southwestern Siberia. The examination of genetic material from this minuscule relic set off new inquiries. to the 2010 finding it indicated the existence of a separate ancient human group, which researchers named the Denisovans.
A significant number of individuals living today possess remnants of Denisovan genetic material. However, due to the scarcity of fossils from these ancient forebears, specialists studying human evolution remain uncertain about their precise appearance, habitat, and reasons for extinction.
Hiding in plain sight?
The challenging-to-categorize Chinese remains consist of 21 fossils discovered in the 1970s at the Xujiayao (also known as Houjiayao) site, which lies on the boundary between northern China’s Shanxi and Hebei provinces. These specimens belong to 16 individuals who inhabited the region approximately 200,000 to 160,000 years ago.
Other notable sites include Lingjing in Xuchang County within central China’s Henan province, where fragments of skulls were discovered from 2007 to 2014, and the northern city of Harbin in Heilongjiang province, where a skull hidden at the base of a well about 90 years ago recently resurfaced.
Many of these fossils had been overlooked because when they were first unearthed in the 1970s and 1980s, commonly held beliefs about human origins were vastly different from today’s theories. Back then, many paleoanthropologists thought that present-day human populations evolved regionally from archaic hominins such as Homo erectus , leaving Africa approximately 2 million years ago. This particular scientific theory, referred to as multiregionalism and mostly dismissed today, proposed that there was just one hominin species that gradually developed into Homo sapiens over time.
In this situation, the Xujiayao remains, along with other specimens featuring peculiar characteristics discovered in China, were categorized as transitional forms linking earlier hominins like Homo erectus to their more advanced counterparts. multiregional scientific model This notion of distinct ancestral origins for the Chinese people aligned with nationalistic feelings and was formerly quite prevalent among scholars in China.
Nevertheless, researchers currently possess compelling genetic proof that backs up an The African origins of all Homo sapiens The currently well-accepted hypothesis is referred to as the "Out of Africa" theory. According to this model, our direct forebears who dwell on Earth today originated from populations within Africa before dispersing across the globe approximately between 50,000 to 60,000 years back. However, some early Homo sapien communities might have ventured out starting roughly 200,000 years ago.
Later findings in Asia and Africa over recent years, including fossils discovered, have shed new light. Homo floresiensis , these small ancient hominins inhabited the region that is now Indonesia's Flores Island between 100,000 and 50,000 years ago, and Homo naledi , similarly small-bodied hominins who resided 300,000 years ago In what is currently South Africa, suggestions have also been made that the current scenario, where just a single species of hominin exists, is uncommon.
"The past 50 years of fossil findings have demonstrated that there was never just one hominin line present at any time in history (highlighting how special modern humans truly are)," stated Carrie Mongle, who is an assistant professor in the Department of Anthropology at Stony Brook University in New York.
Given these considerations, it wouldn't be unwarranted to propose that the count of species associated with the Asian fossils deserves another look—we shouldn't merely suppose that they can all be grouped collectively.
Identifying connections—and counterarguments
According to what they claim is the First "all-encompassing" examination of the Xujiayao remains Bae and Wu managed to create a digital reconstruction of a cranium using the available remains. This skull had an exceptionally broad, low, and wide structure, which set it apart from those of other recognized hominin species like Neanderthals or Homo erectus, and differed significantly from the round skulls characteristic of Homo sapiens, according to their findings. They subsequently compared these characteristics with several enigmatic fossils discovered in the area over the past few years.
The skull was comparable to two atypically big skulls discovered in Xuchang County In Henan province from 2007 to 2014, where the container held a volume of 1,800 cubic centimeters (about 110 cubic inches). The dental remains unearthed at the Xujiayao location were similar to earlier discoveries; these teeth were included within them. a jawbone discovered in the early 1980s On the Tibetan Plateau, at a location where scientists in 2020 discovered Denisovan-linked DNA in cave sediments as well; a tooth discovered in a cave located in Laos Reported in 2022 and linked to Denisovans, these findings were joined by those from a jawbone discovered at an antique shop in Taiwan back in 2008, referred to as the Penghu mandible.
Bae and Wu jointly contend that the hominins associated with these fossilized bone fragments ought to be categorized as Homo juluensis. According to Bae, he was aware that suggesting the incorporation of Denisovan specimens might "stir controversy," yet he feels confident about the strength of their argument.
I believe many individuals would concur with our viewpoint that these fossils ought to be classified collectively. According to the principles of priority, as we were the first to propose this designation, those remains should be attributed to juluensis," stated Bae. "Perhaps because this information is quite new, people are finding it challenging to grasp our suggestion.
Mongle and other paleoanthropologists argue that it's premature to conclusively categorize the Denisovan specimens alongside those found at Xujiayao and label them as members of a new species known as Homo juluensis.
"The primary argument for this team aiming to identify a new species revolves around the shape of the braincase; however, there are currently no Denisovan cranial remains available for comparison with the Xujiayao skull pieces," stated Ryan McRae, a paleoanthropologist from the Smithsonian National Museum of Natural History. McRae did not participate in Bae and Wu’s study.
McRae’s second point against this was the lack of genetic evidence, a tool that is being more frequently employed in determining species categorization.
Typically, archaeologists stumble upon groundbreaking findings when a trowel strikes a skull or another indicative bone within a cave’s interior. Yet, the Denisovans stand out as the initial archaic humans to be recognized in a laboratory setting due to advancements in ancient DNA studies, adding an extra layer of mystery to their story.
So far, all twelve or so known Denisovan bone samples have been mere pieces rather than complete skeletons—none possessing distinct traits sufficient for a specific scientific classification like those used for Homo sapiens or Homo neanderthalensis. Typically, though not necessarily, a newly identified species is marked by the discovery of a skull due to its abundance of defining characteristics.
We regrettably still haven’t determined what Denisovans looked like," McRae stated. "Our knowledge of Denisovans primarily stems from genetic information rather than fossil records; therefore, any comparisons must incorporate a genetic aspect to strengthen the argument that additional Denisovan remains have been discovered.
Enter the ‘Dragon Man’
As per standard scientific procedure, revisiting old fossils is common practice, noted Xijun Ni, a professor affiliated with the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing. While it’s possible that the specimens examined by Bae and Wu might denote an unacknowledged variety of early hominin, Ni opined that based on their current presentation, there wasn't sufficient data for formally categorizing Homo juluensis as a distinct new species—a classification requiring extensive scrutiny. and is often contested .
Nick and Chris Stringer, who leads human origins research at London’s Natural History Museum, propose another theory about how all these prehistoric fragments come together, drawing from their study of an ancient hominin skull. commonly referred to as "Dragon Man." ”
Initially documented in academic papers in 2021, this particular find carries a captivating history. In 1933, along the banks of the Songhua River in Harbin, China, which was under Japanese control during World War II, a person engaged in compulsory labor discovered the skull. This individual safeguarded the artifact beneath a well for over eight decades until he finally disclosed its presence just before passing away.
Stringer mentioned that his collaboration with Ni indicated that many of the fossils classified by Bae as H. juluensis more closely resemble the Harbin skull in terms of morphology. Based on this observation, Stringer concluded that the Xujiayao samples along with the Denisovan remains might be better grouped under Dragon Man. The species has officially been named Homo longi.
"Consequently, the well-maintained Harbin skull could signify an early Denisovan specimen," Stringer stated, noting that additional studies from different groups support this finding. He also mentioned that new research regarding Dragon Man will be released later this year.
Mongle from Stony Brook University acknowledged that various ancient human species might have inhabited Asia. However, she also expressed the view that the fossils identified by Bae as part of the "big heads" group bear resemblance to the Homo longi skull.
"I am in favor of the concept of multiple hominin lineages during the Asian Pleistocene, but I remain somewhat unconvinced about how distinct these fossils are compared to the newly identified Homo longi specimens," she stated.
Bae said that his analysis suggested that the Dragon Man skull is a better match with fossils found at Chinese sites in Dali in Shaanxi province in and Jinniushan, Liaoning province in 1978 and 1984, respectively, to form Homo longi.
What’s in a (species) name?
Ni pointed out that choosing the name for a newly discovered species like Homo juluensis falls to the researchers; however, these names must adhere to the established nomenclature guidelines. International Committee for Zoological Taxonomy . However, there’s no official approval process and whether the species name sticks or not will be a matter of whether other researchers agree and use it in scientific literature.
Ni stressed that the Denisovans are just one recognized group of ancient hominins, so the term—or some variation of it—shouldn't be indiscriminately applied to others like the Xujiayao hominins, even if they ultimately belong to the same species. He compared this misuse to referring to all Europeans as Anglo-Saxons.
"I firmly disagree with the notion that all previously identified Asian Middle Pleistocene hominins, whether named or unnamed, should be classified as Denisovans, since Denisovan merely refers to a specific group," Ni stated.
Bae concurred. "Many Western paleoanthropologists have suggested referring to the Chinese fossils as Denisovans," he stated. "However, for our team, Denisovans does not represent an actual species."
According to McRae, the individual or group who initially gathers sufficient proof to establish the Denisovans as a separate species can choose whichever name they prefer for it.
"Denisovans haven't been formally named as a new species deliberately since there isn't enough comparative material available for classification," explained McRae.
On the positive side, this allows the scientific community to uncover additional fossil evidence supporting the existence of Denisovans before introducing a new species designation. However, conversely, it also means these crucial fossils could be hastily categorized under an inappropriate taxonomy by individuals.
Some paleoanthropologists remain hopeful that once Denisovans receive an official scientific name, "it will pay homage to the type site, Denisova Cave, as well as the widely used nickname 'Denisovans,'" McRae noted, though he admitted there’s “no assurance this will occur.”
The era in question is teeming with fossilized hominins whose physical characteristics are quite "confusing," he noted. While some appear distinctive, others exhibit traits similar to those found in Neanderthals, and yet others show attributes akin to modern humans like us. Many specimens display a mix of these features, as McRae explained.
"Dividing fossils into species too early might hide the true narrative of what was happening globally at that time. Logistically, it becomes extremely challenging to retract such classifications once they have been disseminated, regardless of whether sufficient evidence supports them," he explained.
A previous iteration of this article incorrectly spelled Ryan McRae’s name.
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