They’re not as prevalent as the Neanderthals, and not as unique as the hobbit-like Homo floresiensis, but the Denisovans are slowly coming out of the ancient hominin closet to define their place in the ancestry of modern humans. Named for the Denisova Cave in the Altai Mountains of Siberia where the first fossils were found, the Denisovans also lived in China and DNA studies suggest they mated with homo sapiens populations across Eurasia, the Philippines and New Guinea, but no other hard fossil evidence has been found … until now.
“We have assumed that Denisovans were in Southeast Asia … but we just didn’t have the fossils for it. This one is in the right place at the right time.”
“This one,” according to University of Toronto paleoanthropologist Bence Viola, is a confirmed Denisovan tooth found in a cave filled with bones in the village of Long Gua Pa in northeastern Laos. A village child led archeologists to the cave (now called Tam Ngu Hao 2 cave), where they discovered the ancient remains of rhinoceroses, tapirs, pigs and rodents … and one humanlike molar. That molar eventually made it to the hands of Laura Shackelford, a paleoanthropologist at the University of Illinois, Urbana-Champaign, who explains in a new study in Nature Communications how it was identified.
“We knew it looked kind of human, but not quite right for a modern human.”
That’s probably a good description of the Denisovans as well. Fossil finds in Siberia and China have been limited to teeth, finger bones and a partial mandible, so painting a picture of them is difficult. Another tooth won’t help in that endeavor, but the enamel on this molar along with its unique structure offered near-definitive proof that it once belonged to a young Denisovan female, aged between 3.5 and 8.5 years old, who lived in what is now Southeast Asia between 164,000 and 131,000 years ago. Is this single tooth a big deal? The study has the answer.
“This discovery further attests that this region was a hotspot of diversity for the genus Homo, with the presence of at least five late Middle to Late Pleistocene species: H. erectus, Denisovans/Neanderthals, H. floresiensis, H. luzonensis and H. sapiens.”
You may have noticed that the study’s list did not include the Neanderthals separately. While the tooth puts those five different Homo species living in close proximity, if not together and interbreeding, around 200,000 years ago, Neanderthals were thouht to still in Western Europe at that time. Because teeth are so difficult to confirm, Katerina Douka, an assistant professor of archaeological science at the department of evolutionary anthropology at the University of Vienna and not a part of the study, told CNN that she and others hesitate to accept unequivocally that it’s Denisovan – holding out the possibility that it could instead be Neanderthal, which would make it the earliest evidence of that Homo species in Southeast Asia.
“No additional sampling for ancient DNA analyses is performed at this stage given the old age of the specimen and the tropical conditions under which the sediment and fossils were deposited.”
The study’s authors seem to be listening to Douka – they plan to try and extract some ancient DNA to confirm their analysis. More importantly, they plan to return to Laos to the Tam Ngu Hao 2 cave and others in order to dig for more of the elusive teeth, bones and other fossil remains of Denisovans, who are proving to be quite an interesting species of ancient humans. As Dr. Fabrice Demeter, lead study author and assistant professor of paleoanthropology at the University of Copenhagen, explained to IFLScience.
“Our study shows that Denisovans lived in a wide range of environments and latitudes, and were able to adapt to extreme conditions, from the cold mountains of the Altai and Tibet to the tropical forests of Southeast Asia.”
High altitudes, cold climates, low altitudes, warm and humid climates – it didn’t’ seem to matter to the Denisovans. This new discovery may one day help show how important they were in the making of modern humans.