Denisova Cave in southern Siberia is one of the hottest sites within palaeoanthropology. It was in this cave that an archaic, yet poorly understood, human species was first identified: the Denisovans. But other species were known to occupy the site, too. How, when?
Since only eight human bone fragments have come from the cave, Michael Shunkov of the Russian Academy of Sciences assembled a team of archaeologists, geneticists, and others to study the DNA from the cave sediments and also combine it with other sources of evidence. Examining 728 samples from the cave took two years. In the end, 175 of them yielded human DNA, revealing astounding details of changing human occupation within the site over a lengthy period.
When the scientists matched the DNA with the ages of the cave layers, they found that the earliest DNA was that of the Denisovans, who fabricated the earliest stone tools at the site between 250,000 and 170,000 years ago. The first Neanderthals (pictured) entered the site about 190,000 years ago, when the local climate turned colder, in contrast to earlier warmer, interglacial conditions. This colder period was when both Denisovans and Neanderthals visited the site. But between 130,000 and 100,000 years ago, there were no Denisovans in the samples, as if they had moved away during another warmer period. After 100,000 years ago, they returned, but with changed mitochondrial (mother-inherited) DNA – perhaps signs of a different Denisovan population arriving in the region. Entirely modern (Homo sapiens) DNA first appears around 45,000 years ago, at a time when toolkits in the cave became much more diverse.
This research is just the beginning, but it ushers in a new era of palaeoanthropology that will revolutionize our knowledge of human evolution.
Model of a Neanderthal, on show at London’s Natural History Museum.
Image: Allan Henderson/CC BY 2.0