A reconstruction of Homo longi
Chuang Zhao
A large fossil skull discovered in China may belong to one of our mysterious long-lost relatives, the Denisovans, potentially offering us our first glimpse of a Denisovan face. It has, however, been placed in a new human species – Homo longi – a name that derives from a Chinese term meaning “dragon”, and that means the early hominin may become known informally as “dragon man”.
Other researchers say the discovery is important and exciting, but think the decision to add a new species to our family tree is premature.
The Harbin cranium was discovered in mysterious circumstances in Harbin City in the Heilongjiang province of China in the 1930s. The man who unearthed it reportedly hid it in a well, only revealing its location on his deathbed. It was recovered in 2018 and has now been analysed for the first time.
“It’s a really amazing discovery. It is one of the most complete crania I have ever seen,” says Xijun Ni at the Chinese Academy of Sciences, who was part of the team that studied the fossil. It is also the largest known Homo skull ever found.
“This is the biggest human skull I’ve seen – and I’ve seen a few,” says Chris Stringer at the Natural History Museum, London, who was also a member of the team.
The researchers estimate that the skull belonged to a man who was about 50 years old when he died, between 146,000 and 296,000 years ago. Its features are a mix of those seen in archaic and modern humans. It has thick brow ridges, for example, yet “the face looks so much like a bigger version of a modern human face”, says Stringer. Its brain size was similar to ours too.
“It’s got such an interesting combination of features,” says Stringer. “The morphology shows that this is definitely a distinct lineage in eastern Asia. It’s not Neanderthal and it’s not Homo sapiens, it’s something quite distinctive,” says Stringer.
One possibility is that the Harbin fossil is a Denisovan. This mysterious group of extinct humans was first identified a decade ago from DNA in a finger bone found in the Denisova cave in Siberia, Russia. The Denisovans were closely related to the Neanderthals, and lived in Asia for hundreds of thousands of years. They also interbred with H. sapiens.
A few additional Denisovan fossils been identified in recent years, including a jawbone at least 160,000 years old from Tibet, known as the Xiahe mandible. But Denisovan skulls have proved more difficult to track down: the Harbin cranium may be one of the strongest candidates yet found, bringing us closer to our first definitive glimpse of a Denisovan face.
When a team led by Ni constructed a family tree to establish the ancestral lineage of the Harbin fossil, based on physical characteristics of the fossils, they found that it was most closely related to the Xiahe mandible. Interestingly, both of these fossils have massive teeth.
“What’s remarkable about the Denisovans to me is the size of their teeth,” says Shara Bailey at New York University, who wasn’t involved with the study. “It’s an exciting possibility that [the Harbin cranium] could be our first Denisovan skull. It could be the face of a Denisovan.”
John Hawks at the University of Wisconsin-Madison agrees. “My opinion is that… this is more than likely Denisovan.”
The clincher would be if DNA could be extracted from the Harbin cranium, something that may be done in future.
“I think it’s possible that Harbin will turn out to be a Denisovan skull, the most complete one,” says Stringer. “That’s something we’ll have to test with DNA, but that’s probably a long shot because it’s at least 146,000 years old.”
Although there is excitement at the possibility that the Harbin skull might be Denisovan, there is less enthusiasm about the decision to officially name it as a new species. Five members of the research team, including Ni – but not Stringer – co-authored an accompanying paper in which they established it as H. longi.
Many researchers prefer not to name new human species for several reasons, including the fact that DNA evidence shows that “species”, including Neanderthals and Homo sapiens, interbred. Most academics prefer to refer to the Denisovans as a “group” or “lineage” rather than a distinct species. “You can be a separate lineage and not have achieved species status,” says Bailey.
“I do think that the one type of analysis they use isn’t conclusive enough to say that there’s a new species,” says Sheela Athreya at Texas A&M University.
Journal references: The Innovation, DOI: 10.1016/j.xinn.2021.100130 and DOI: 10.1016/j.xinn.2021.100132
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Source: Humans - newscientist.com
