The pandemic shutdown has taught us that it’s difficult to stay inside one’s home for an extended period with one’s immediate family. It was more difficult for those living with extended family and/or friends. Now, think of how challenging, frustrating and even murder-enticing it might be to have to live with people of other species – and the offspring of mixed-species marriages. That’s the new story of the famous Denisova cave in southern Siberia, where researchers previously discovered a new archaic hominin species, the Denisovans, living with another archaic hominin species, the Neanderthals, and now have found both shared the cave with a third hominin species – humans. All at the same time! How did they get along? Was the evidence discovered an archaic boxing ring?
“Denisova Cave in southern Siberia is the type locality of the Denisovans, an archaic hominin group who were related to Neanderthals. The dozen hominin remains recovered from the deposits also include Neanderthals, and the child of a Neanderthal and a Denisovan, which suggests that Denisova Cave was a contact zone between these archaic hominins.”
The determination that Denisovans and Neanderthals occupied the Denisova cave at the same time came from the discovery of just eight fossils – including a Denisovan pinkie, three bones from Neanderthals and one from a child with one Neanderthal and one Denisovan parent. That’s the frustratingly tiny total after archeologists have combed through piles of animal bones and fossils mixed with stone tools and artifacts. As Science Magazine explains, researchers like Elena Zavala, a graduate student at the Max Planck Institute for Evolutionary Anthropology, turned to analyzing the layers of sediment in the three-chamber cave and looking for DNA. What they found, as explained in a new study in the journal Nature co-authored by Zavala, has added crucial data to the history of humans.
“We detect a turnover in the mtDNA of Denisovans that coincides with changes in the composition of faunal mtDNA, and evidence that Denisovans and Neanderthals occupied the site repeatedly—possibly until, or after, the onset of the Initial Upper Palaeolithic at least 45,000 years ago, when modern human mtDNA is first recorded in the sediments.”
After 2 years of analyzing 728 sediment samples dating to the Pleistocene epoch, they found ancient hominin mitochondrial DNA in 175 of them. Human mitochondrial DNA (mtDNA) is the DNA located in cellular organelles that convert chemical energy from food into a form that cells can use. It’s part of the human genome and recognized by anthropologists as the next best thing to bone samples, and in this case the mtDNA samples far exceed the fossilized bone fragments found.
Yes, this discovery affects human history in a big way. It confirms that a first group of Denisovans occupied the cave about 300,000 to 130,000 years ago. A second came in about 30,000 years later. Neanderthals moved in around 170,000 years ago – again with different groups occupying and leaving the cave. What the newly discovered mtDNA shows is modern humans living there about 45,000 years ago and the soil layer from that period contains DNA from all three human groups. Katerina Douka, an archaeological scientist at the Max Planck Institute for the Science of Human History who was not involved with the research, puts it best:
“I cannot think of another site where three human species lived through time.”
Not only that, the existence of Denisovans was not known until 2010! The ability to identify mtDNA is the game-changer. The study concludes with that acknowledgement.
“High-resolution profiling of sediment DNA can therefore provide an effective means of filling gaps in our knowledge of human evolutionary history and palaeoecology, independent of the discovery of skeletal remains.”
Does this change our history? Of course not – our history already happened and there’s nothing we can do to change it. (Keep that in mind during your next political discussion.) All we can do is acknowledge that our records of it have huge gaps of reliable data and we must continue our search for more. Our history books should be looked at as constantly-updated, ever-growing chronicles, not stone tablets.
How long before our ancestry DNA tests go back to the Denisovan cave? It may be sooner than you think.