Siberian cave reveals oldest fossils belonging to enigmatic human species

The entrance to the Denisova cave in Sibera.

The entrance to the Denisova cave in Sibera.
Picture: IAET, Siberian branch of the Russian Academy of Sciences

The Denisovans, a mysterious group of extinct hominids closely related to the Neanderthals, didn’t leave much fossil evidence behind. A further excavation of their former trampling grounds in Siberia has now yielded three new fossils, the oldest ever of this species.

Katerina Douka, an evolutionary anthropologist at the University of Vienna, and her colleagues found the fossils in Denisova Cave, a natural shelter located in the Altai Mountains in southern Siberia. Scientists were studying the oldest layers of the cave, which until now had failed to produce a single human fossil. A total of five human fossil fragments were recovered: three belonging to Denisovans, one to a Neanderthal and one that could not be identified. The largest of these fragments is no more than 1.6 inches (4 centimeters) long.

Remarkably, this small but precious handful of fossils was found amid a jumble of 3,791 animal bone fragments. The researchers used a biomolecular method known as a peptide fingerprint to identify the bones because it was not possible to do this by manual inspection. All five bones contained collagen consistent with human peptide profiles (peptides are the building blocks of proteins), allowing identification (as a reminder, Denisovans and Neanderthals are humans).

Some of the bone fragments recovered from the Denisova cave.

Some of the bone fragments recovered from the Denisova cave.
Picture: S. Brown

“Finding a new human bone would have been cool, but five? It exceeded my wildest dreams, ”said Samantha Brown, study co-author and junior group leader at the University of Tübingen, in a Max Planck Institute declaration.

Denisova Cave is an “amazing place” when it comes to DNA preservation, and “we have now reconstructed the genomes of some of the oldest and best preserved human fossils,” said Diyendo Massilani, geneticist at the ‘Max Planck Institute for Evolution. Anthropology, in the press release. The team found enough DNA to reconstruct the mitochondrial genomes, which allowed them to confirm that the bones belonged to the Denisovans and Neanderthals. A paper detailing this discovery has been published in Nature Ecology & Evolution.

The layer containing Denisovan’s bones was dated to around 200,000 years ago. The ancient Denisovan fossils were dated between 122,000 and 194,000 years ago, so they are now the oldest. The only Neanderthal bone was dated to between 130,000 and 150,000 years ago. The Altai Mountains appear “to have been an area of ​​overlap for the Denisovan and Neanderthal groups for over 150,000 years, testifying and possibly facilitating the population. [interbreeding] as well as maintaining distinct hominid populations over that long period, ”according to the document.

The three new Denisovan fossils are added to the six already discovered, including one finger bone whose DNA was extracted and a mandible found in a cave on the Tibetan plateau – the first and only Denisovan fossil found outside Siberia. The Denisovans were closely related to the Neanderthals and they interbreeded with modern humans before disappearing around 50,000 to 30,000 years ago. Traces of Denisovan DNA exist in the genomes of modern populations in Southeast Asia and Oceania.

As the scientists write in their study, “a wealth of archaeological material” in the form of stone tools and animal remains has been found in the Denisovan layer. This is the first time that archaeological evidence is definitively linked to these hominids, allowing new knowledge about their behavior.

It is interesting to note that the style of the stone tools recovered, such as the scraping tools for working with animal skins, could not correspond to any known lithic tradition. Living near the Anui River and occupying the caves during a hot period, the Denisovans hunted bison, deer, gazelle, antelope, and woolly rhino, on a livelihood that spanned thousands of years, such as the researchers point out.

These three Denisovan bones will likely produce more science in the years to come, as will Denisova Cave in general. Slowly but very methodically, we discover more about these remarkable humans.

Following: Scientists have discovered a Denisovan ancestor hotspot.

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