A team of researchers working in Denisova Cave located in the Altai Krai region of Russia have conducted “the most comprehensive study yet of ancient DNA extracted from sediment at any single site in the world,” as they explained an article published on The Conversation website.
The scientists were able to extract mitochondrial DNA from over 700 samples and to “anchor” them to “a timeline for Denisova Cave, generating a detailed picture of which humans and animals were present at this famous site at various times in the past.”
"The analysis of sediment DNA provides a wonderful opportunity to combine the dates that we previously determined for the deposits in Denisova Cave with molecular evidence for the presence of people and fauna," Richard "Bert" Roberts from the University of Wollongong said as quoted by EurekAlert.
Elena Zavala of the Max Planck Institute for Evolutionary Anthropology, lead author of the study, has revealed that they "detected the DNA of Denisovans, Neandertals or ancient modern humans in 175 of the samples."
The researchers established that the earliest hominin DNA belonged to Denisovans – a long-extinct form of archaic human "thought to have occupied large parts of central and eastern Asia" – who are supposedly made the oldest stone tools discovered at the site, between 250,000 and 170,000 years ago.
Around the end of that time, the Neanderthals arrived at the site, and both they frequented the site along with the Denisovans, though no DNA related to the latter group was found in the sediment dating between 130,000 and 100,000 years ago.
The modern human mitochondrial DNA only makes its first appearance “in the layers containing Initial Upper Palaeolithic tools and other objects,” as EurekAlert puts it, with said layers appearing more diverse than the previous ones.
"This provides not only the first evidence of ancient modern humans at the site, but also suggests that they may have brought new technology into the region with them," Zavala said.
Matthias Meyer, also from the Max Planck Institute for Evolutionary Anthropology and senior author on the study, remarked that "being able to generate such dense genetic data from an archaeological site is like a dream come true," adding that "these are just the beginnings."
"There is so much information hidden in sediments – it will keep us and many other geneticists busy for a lifetime," he remarked.