2023 Author: Bryan Walter | [email protected]. Last modified: 2023-05-21 22:24
Excavation in the southern chamber of Denisova cave
Paleogeneticists analyzed 728 sediment samples from Denisova Cave and found fragments of mitochondrial DNA from Denisovans in 79 samples, and Neanderthals in 47 samples. The oldest biological material belonged to Homo denisovensis. It was found in a sample from a cultural layer dating back to 294-206 thousand years ago. Scientists have found that various lineages of Neanderthals came to the site later, but in some long periods remained the only population of people in Denisova Cave. The research results are published in the journal Nature.
Denisova Cave is located on the territory of the Soloneshensky District of the Altai Territory in the valley of the Anuy River. The first archaeological work here was carried out back in 1978 by Academician Okladnikov and continues to this day. At different times, Neanderthals and the ancestors of modern people lived here. The site gained worldwide fame after the publication in 2010 in the journal Nature of the results of genetic studies of the ancient phalanx of the little finger of a child who turned out to be a representative of a previously unknown species - Homo denisovensis.
Location of Denisova Cave and its schematic structure
During the work, archaeologists were able to find fragments of the bones of five Denisovans, and the mother of one of them was a Neanderthal. Subsequently, the remains of Homo denisovensis were also identified in the Tibetan Baishiya Cave. The most ancient cultural layers in the Altai cave were probably Denisovian. A 2019 study showed that they lived in the cave 287-51 thousand years ago, and the Neanderthals - 193-79 thousand years ago. However, these data are regularly shifted and refined in different directions. In addition, they do not indicate periods of permanent residence, since at different times the cave was inhabited by genetically distant populations of ancient people, which is also typical for neighboring sites.
Elena Zavala of the Max Planck Institute for Evolutionary Anthropology, together with scientists from Australia, Russia and Israel, analyzed 728 sediment samples from Denisova Cave to extract DNA from them. They pursued the goal of discovering the biological material of the ancient representatives of Homo and fauna, in order to reconstruct in detail the sequence of the settlement of the site by people.
Geneticists were able to identify mitochondrial DNA of ancient mammals in 685 samples (94 percent) from all selected layers, including those older than 290 thousand years. Mitochondrial DNA of ancient people was found in 175 samples (24 percent), belonging to almost all layers of the three chambers of the cave.
View of the Denisov cave
During the research, scientists were able to identify several lines of Neanderthals living in Denisova Cave. The first goes back to the remains from the Sierra de Atapuerca site in Spain, dating back to 430 thousand years ago. The second - to the finds from the Holenstein-Stadel cave in Germany. The third line is the most common, known from all other Neanderthals. In total, Denisovan material was contained in 79 samples, and Neanderthal - in 47. In addition, scientists discovered fragments of mitochondrial DNA that belonged to a previously unknown line of Neanderthals, which deviated from the main line about 255-230 thousand years ago.
The oldest recovered human mitochondrial DNA belonged to a Denisovite. It was found in a sample from the 21st layer of the main chamber, dating back to 250 ± 44 thousand years ago. Researchers have established that the deposits of the Early Middle Paleolithic with an antiquity of more than 170 ± 19 thousand years belong precisely to the Denisovians. However, in samples dating back to 130-100 thousand years ago, only the genetic material of Neanderthals is present, and sequences similar to Denisov-11 appear in the sediments after 80 thousand years ago.
Archaeological work in the southern chamber of Denisova cave
Geneticists also looked at ancient fauna, the DNA of which was found in the samples. They confirmed the presence of the camel Knobloch (Camelus knoblochi) in the Pleistocene layers. Changes in the relative abundance of mammals over time are consistent with known data for bovids (Bovidae), hyenas (Hyaenidae), canines (Canidae), and bears (Ursidae). The mitochondrial DNA of elephants (Elephantidae) belongs in all layers to the woolly mammoth (Mammuthus primigenius). The cave bear (Ursus spelaeus), which dominated the layers older than 187 thousand years, was replaced by the brown bear (Ursus arctos) by 112 thousand years ago. Scientists have also discovered three different mitochondrial DNA haplogroups related to spotted and cave hyenas (Crocuta). Thus, Altai was a contact zone not only for different types of people, but also for other fauna.
As a result of the research, scientists noted that fragments of mitochondrial DNA extracted from the layers of the Middle Paleolithic (after 80 thousand years ago) demonstrate genetic affinity not only with Denisov-3 and Denisov-4, but also with the find in the Tibetan cave of Baishiya. Geneticists suggested that Pleistocene mammals migrated from Southeast Asia along the eastern foothills of the Himalayas to Northwestern Altai. This could stimulate the Denisovites to follow them. In addition, the discovered mitochondrial DNA of Neanderthals limits the period of obtaining genes from mixing with the early ancestors of modern humans 430-170 thousand years ago.
New research on Denisovans on N + 1 is not bypassed. Earlier we said that people of the modern type interbred with Denisovans twice, and statistical analysis pushed the time of the discrepancy between Neanderthals and Denisovans.