Fossils found in Chinese cave have identity revealed by DNA analysis

A mystery surrounding human fossils found in a cave in China has been solved by DNA sequencing, according to a new study, and could open the door to discussions about the ancestry of early Americans.

In 1989, a thigh bone and part of a skull were found in a cave in China’s southwestern province of Yunnan.

Radiocarbon dating performed in 2008 on the sediments where the fossils were found indicated that they were around 14,000 years old — meaning they were from a time period when Homo sapiens (modern humans) had migrated to many parts of the world. world.

However, the bones’ primitive features troubled scientists, who questioned what species of human the fossils belonged to.

The skull’s shape resembled that of Neanderthals — an archaic human population that disappeared around 40,000 years ago — and it looked like the brain would be smaller than that of modern humans.

As a result, some experts in human evolution thought the skull likely belonged to a hybrid population of archaic and modern humans or perhaps to a previously unknown human species that existed alongside our own. Researchers named the group the Red Deer People after the name of the cave in which the remains were found.

Now, Chinese scientists have extracted genetic material from the skullcap and sequenced the DNA. They found that the skull belonged to a female individual, who was likely a direct human ancestor—a member of Homo sapiens—and not a previously unknown type of human.

“The ancient DNA technique is a really powerful tool,” said Bing Su, a professor at the Kunming Institute of Zoology at the Chinese Academy of Sciences in Yunnan, who was involved in the research, in a press release.

“This definitely tells us that the Red Deer Cave people were modern humans rather than an archaic species such as Neanderthals or Denisovans, despite their unusual morphological features.”

Su and his colleagues shared their findings in a study published Thursday in the journal Current Biology.

Genome analysis revealed that the individual to which the bones belonged had levels of Neanderthal and Denisovan ancestry similar to those found in modern humans — suggesting they were not part of a hybrid population that interbred with each other.

The DNA of Denisovans, a poorly understood group of archaic humans, and Neanderthals lives on in some humans today. That’s because long ago our Homo sapiens ancestors encountered these groups as they spread across the world and reproduced with them.

First Americans?

Researchers compared the genome extracted from ancient DNA with the genomes of other people from around the world — modern and ancient.

They found that the bones belonged to an individual who was deeply connected to East Asian Native American ancestry.

Scientists believe that this group of people traveled to northern Siberia and then crossed the Bering Strait to become one of the first Americans.

“Its genome fills in a really important missing part of the overall story of how humans arrived in the Americas. Much work has focused on the other branch of Native American ancestry — the Siberians — but not much was known until this article about the ancestors of East Asian Native Americans. It is really important to understand this branch as it is responsible for most of the ancestors of Native Americans!” Jennifer Raff, a geneticist and anthropologist at the University of Kansas and author of “Origin: A Genetic History of the Americas,” said via email.

“I find their results plausible and very interesting. We’re still trying to figure out the geographic location of the immediate ancestral population of the First Peoples, but this paper gives us some additional clues,” added Raff, who was not involved in the research.

Robust features

But what explains the unusual morphological features of the remains?

The researchers described the genome as “low coverage,” meaning it doesn’t contain enough detail to offer an explanation for why the bones looked different from modern human skeletons.

Acidic soil and hot, humid conditions where the skull was found meant that scientists were only able to recover 11.3% of the genome. It was the first time DNA had been sequenced from a human fossil found in southern China.

The study noted that the individual to which the bones belonged had a lot of genetic diversity, indicating that several different lineages of modern humans must have coexisted in South East Asia during the Late Stone Age. Perhaps, the study suggested, the region was a refuge during the height of the Ice Age.

Darren Curnoe, a research associate at the Australian Museum Research Institute in Sydney, said that in 2012 he published the first international scientific paper on the fossils, which he described as having a “very robust anatomy”.

“I know these fossils better than anyone. They are anatomically very intriguing, even if they are modern humans, as the DNA suggests,” Curnoe, who was not involved in the latest study, said via email.

“How can we reconcile this? Perhaps the anatomical shape of people in the past — over long time scales — was too ‘plastic’ and responded to the environment and lifestyle of these primitive people. This could be something we’ve missed since we started farming.”

Analysis of the Red Deer Cave genome could also help build a more complete picture of ancient humans in East and Southeast Asia — an interesting site for paleoanthropologists.

It is where some of the oldest rock art in the world has been found and intriguing archaic human remains such as the Flower Hobbits in Indonesia and the Dragon Man in northern China have been discovered. Other discoveries are unraveling mysteries about Denisovans.

As a next step, the Chinese team hopes to find additional support for their findings by sequencing older human DNA using fossils from South East Asia, especially those that predated the Red Deer Cave people.