Neanderthals: Expert discusses why species went extinct
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An international team led by researchers from German and Italian institutions has identified five new human fossils in the famous Denisova Cave in the Altai Mountains, Siberia. The fossils have been described as the oldest-known remains of a prehistoric human lineage known as the Denisovans. On the evolutionary tree, the Denisovans or Denisova are an extinct hominin species that thrived across Asia during the Lower and Middle Paleolithic (Old Stone Age).
Very little is known about this species and what scientists have discovered to date is based mostly on DNA analysis.
But the new discovery is bound to shed some light on the prehistoric species and scientists are excited to properly analyse the fossils.
The remains, which include three Denisovans and one Neanderthal, have been dated to about 200,000 years ago.
They were found among other items of interest, including stone tools and food use, giving some insight into the “adaptation strategies of these early hominins as they spread across Eurasia”.
Denisova Cave sits in the Altai Mountains in southern Siberia where 11 years ago scientists unearthed the first evidence of the Denisovan species.
This happened when they analysed the genetic material of a pinky bone, revealing in the process a previously unknown human group.
And yet, according to the Max Planck Institute in Germany, scientists have struggled to make any major Denisova fossil discoveries since.
The remains are “extremely fragmentary and difficult to spot” among the animal bones littering the cave.
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And without access to a proper set of fossils, scientists are unable to learn about when the Denisovans arrived at the site, lived and interacted with each other.
The researchers were, consequently, absolutely thrilled to have found not one but three sets of new Denisovan fossils.
Samantha Brown, a doctoral student with Katerina Douka at the Department of Evolutionary Anthropology of the University of Vienna, said: “Finding one new human bone would have been cool, but five? This exceeded my wildest dreams.”
Professor Douka added: “We were stunned to discover new human bone fragments preserving intact biomolecules from such ancient layers.”
The researcher, together with colleagues in Germany and Russia, extracted and analysed protein and DNA samples from nearly 4,0000 bone fragments recovered in the cave.
Using a technique called peptide fingerprinting, or ZooMS (Zooarchaeology by Mass Spectroscopy), they focused on the oldest layer of material dating back as early 200,000 years ago.
Until now, scientists have been unable to find any human layers in this later.
After analysing some 3,800 fragments measuring no more than 1.5 inches in length, Ms Brown identified five bones matching the profile of a human.
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Of these five fragments, four contained enough DNA to reconstruct their mitochondrial genomes.
Three of these were found to align with the genetic makeup of Densivoans and one of the Neanderthals.
And because the fossils have been dated to 200,000 years ago, they represent the oldest-known remains of the Denisovan species.
Dr Diyendo Massilani, a postdoctoral researcher from the Max Planck Institute of Evolutionary Anthropology in Leipzig, said: “Denisova is an amazing place for aDNA preservation, and we have now reconstructed genomes from some of the oldest and best-preserved human fossils.”
Team member Professor Tom Higham, University of Vienna, added: “The application of biomolecular fingerprinting like the one we have applied at Denisova has allowed us to find more human fossils than through formal archaeological excavation.
“It is a tremendous technical breakthrough for Palaeolithic archaeology.”
Although evidence is limited, it appears as though the Denisovans existed up until about 14,500 years ago.
There is also some evidence of interbreeding between the Denisovans and Neanderthals, and a small section of the Denisovan genetic code belongs to another unknown species of ancient human.
The new findings were published in the journal Nature Ecology and Evolution.
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