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A 300,000-year-old fossil raises questions about human evolution

A 300,000-year-old fossil raises questions about human evolution

An interesting hominin fossil discovered in China suggests new scenarios about the evolution of our ancestors.

The human family tree is full of surprises, especially when we look at Asia. Paleontologists have discovered many fossils there, surprising in their shape and diversity. A recent discoverydescribed in Journal of Human EvolutionIt adds a piece to this puzzle. Neither ancient nor modern “mosaic” ancestors can connect our ancestors to more primitive lineages. Even representing an unknown lineage!

At least that’s what the team, which analyzed a skull and jaw excavated a few years ago in Hualongdong, eastern China, says. These bones, called HLD 6, are those of a 12 or 13-year-old young man who lived 300,000 years ago, or about 200,000 years before that.Homo sapiens It does not reach Asia, coming from Africa (according to the most accepted theory).

But here it is: HLD 6’s properties are “unexpected,” according to the Sino-Spanish team, which compared it to several other fossils. The absence of a chin, among other subtle anatomical details, makes the specimen more like a specimen Homo erectuswho occupied the area for a very long time. But some aspects, particularly the angle of the lower jaw and teeth, are more reminiscent of the former Homo sapiensThe skull confirms that the face was flat, without a prominent eyebrow bone.

In short, this fossil is mysterious… and unclassifiable! Which does not surprise Michele Drapeau, a professor in the Department of Anthropology at the University of Montreal. “In reality, we don’t really understand the history of hominins in Asia,” she points out. “Many of the specimens found there have intermediate forms, and we are having difficulty fitting them into models established for Africa and Europe.”

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According to these models, “modern” humans appeared in Africa about 300,000 years ago. They then spread to the rest of the world, and did not settle in China until later. The Hualongdong fossil could mean that anatomically modern (or rather modern-looking) humans appeared independently in Asia, alongside their African counterparts. Serious rewriting of the script!

“Wu Liu Team [auteur principal de la publication] He defends the idea that there were several independent dynasties in China. for the first time Homo erectus, Neanderthals, then Denisovans who arrived there about 400 thousand years before our era. The hypothesis of a third lineage to which HLD 6 belongs is accepted. There are other fossils in China that look very different from Homo erectus or Denisovans, which is interesting! » Comments by Bence Viola, paleontologist at the University of Toronto.

the “Dali’s skull”260,000 years ago, has also been presented as a possible transitional period between Homo erectus And Homo sapiens, in 2017. But, according to Pence Viola, the fact that this possible third lineage led to anatomically modern human beings is more controversial. “Fossils and genetic data clearly show thisHomo sapiens Comes from Africa. »

Who was first?

The scientific community is reluctant to comment on these mysterious hybrids. “There are many problems with most of the materials found in China,” the expert continues. First, until very recently, results were only published in Chinese; Second, there are no accessible sample templates. Finally, dating can be unreliable. Therefore, developing sophisticated scenarios is complex. »

Although he considers this fossil “very interesting,” Pence Viola asserts that it is incomplete. “Many measurements have been extrapolated from the parts that have been found. We have nothing about the occiput, for example, which is important from a genetic evolutionary perspective.”

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For her part, Michele Drapeau warns against an overly simplistic association between facial prowess and modernity. “This is correctHomo sapiensIn almost all characteristics, they are smaller than Neanderthals, Neanderthals, and Denisovans. So, when we see thinner features on a fossil, we tend to say it drifted toward it Homo sapiens. But some colleagues argue that thin features are actually primitive, and come from… Homo erectus She explains that Africans, and the huge faces of other races, would be derived from these slender features. Perhaps this teenager’s beautiful features reflect his antiquity rather than his modernity…

One thing is certain: human evolution was not linear, and many forms, species and hybrids coexisted. The researcher summarizes: “Some characteristics gradually became clearer, but there is no clear line, so it is difficult to classify the fossil into a specific type.”

If every bone is subject to interpretation, it can also be exploited, as Pence Viola warns. “For the Chinese government, the narrative that people’s ancestors have been in the land for hundreds of thousands of years is important. It’s political, it reinforces the idea of ​​nationhood.” He hopes that genetic analyzes will one day make these fossils speak objectively.