The Annals of DNA
300 thousand years of life of the inhabitants of the Altai Denisova cave
The material was prepared according to the press release of the Max Planck Society Institute for Evolutionary Anthropology (Pleistocene sediment DNA from Denisova Cave).
The research of DNA extracted from fossil bone remains marked a real revolution in the study of the ancient history of mankind. However, the number of such anthropological finds is small, and today scientists use human DNA preserved in sedimentary deposits of caves where ancient people lived to reconstruct historical events.
The Denisova karst Cave, located in the Altai Mountains, has become widely known in recent years as a unique archaeological monument. Judging by the data of archaeologists and paleogeneticists, it served as a home for ancient man for 300 thousand years!
During this unimaginably long period of time, a variety of representatives of humanity, including Neanderthals, lived here. And about ten years ago, the remains of a previously unknown archaic man, called a Denisovan, were found in the cave, who, as a result of paleogenetic and genetic studies, received the "legal status" of our ancestor.
Another striking finding was a direct confirmation of the close ties between different groups of archaic people – a tiny piece of bone of a child whose mother turned out to be a Neanderthal and whose father was a Denisovan. Considering that very few human fossils have been found in the Denisova Cave, the discovery of such a hybrid suggests that interbreeding between representatives of different populations of ancient people was commonplace.
Professor S. Paabo from the Institute of Evolutionary Anthropology of the Max Planck Society (Germany) talks about deciphering ancient DNA from the fossil bone remains of Denisov man (Gorny Altai, 2018). On the right is a fragment of a fossil bone about 2.5 cm long from the eastern gallery of the Denisova Cave, more than 50 thousand years old, belonging to a half-breed girl – the daughter of a Neanderthal and a Denisovan. Photo by T. Hayam.
All these sensational discoveries were made based on the analysis of ancient DNA isolated from very small bone fragments, extremely uninformative from the point of view of anthropology. But if the species belonging of the "owner" of the sample can still be proved, then it is almost impossible to associate certain types of stone tools and other artifacts with specific groups of people. Thus, the discovery of jewelry typical of the beginning of the Upper Paleolithic in the layers of cave deposits about 45 thousand years old caused heated debates about who their creators were: Denisovans, Neanderthals or people of the modern physical type.
The way out of the impasse caused by the lack of material can be the analysis of DNA extracted directly from the sedimentary rocks of the cave. Paleogeneticists managed to isolate and analyze the mitochondrial DNA of an ancient person from such samples a few years ago, and later it was the turn of nuclear DNA.
About 170 dating data have already been obtained for the Paleolithic layers of Denisova Cave using various methods in laboratories in Europe and the USA. The photo shows the sampling for OSL dating in the central hall of the cave. Photo by S. Zelensky.
Recently, scientists from an interdisciplinary group that includes archaeologists, geneticists, geochronologists and other specialists from the Max Planck Society Institute for Evolutionary Anthropology (Germany) and the Siberian Branch of the Russian Academy of Sciences published a paper where they presented an analysis of mitochondrial DNA from 728 samples of sedimentary deposits of Denisova Cave – the largest study in this field today.
Article by Zavala et al. Pleistocene sediment DNA reveals hominin and faunal turnovers at Denisova Cave published in the journal Nature – VM.
In two years of work, scientists have managed to find 175 DNA samples of Denisovans, Neanderthals and ancient people of modern type. Comparing these results with the age of the layers from which the samples were extracted, scientists found out that about 250-170 thousand years ago the Denisovans inhabited the cave – the oldest stone tools in the cave turned out to be their handiwork. Towards the end of this period, Neanderthals began to appear in the cave, along with Denisovans.
About 130 thousand years ago, the "genetic traces" of Denisovans from the cave completely disappeared and appeared only after several tens of thousands of years. But these were, judging by the DNA, already "other" Denisovans.
Human DNA of a modern physical type was found in layers of sediments corresponding to the time of the emergence of the archaeological culture of the beginning of the Upper Paleolithic, i.e. about 45 thousand years ago. The tools that were found in them indicate that these people brought new technologies with them.
Typical products of the early stage of the Upper Paleolithic discovered in the 11th layer of the southern gallery of the Denisova cave (aged 50-40 thousand years): beads made of marble, talc and serpentine (above), a fragment of a pendant made of a tooth and pierced animal bones (below). Photo by A. Fedorchenko.
The data obtained during the analysis of animal DNA also added curious touches to the overall picture. For example, in the populations of hyenas and bears, changes were noted associated with the appearance of Neanderthals in the cave about 190 thousand years ago, when the relatively warm climate changed to a cold glacial one, as well as with the disappearance of the first group of Denisovans – at that time the climate warmed up again.
Thus, even where scientists have managed to extract ancient human DNA directly from fossil human bones, the study of sedimentary rocks can provide surprisingly much new information. And this new approach incredibly expands the range of possibilities of paleogenetics.
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