New Studies Reveal Deep History of Denisovans and Neanderthals in Southern Siberia
Denisova Cave is the only site in the world known to have been occupied by both Denisovans and Neanderthals at various times. Two new studies published in the journal Nature, now put a timeline on when the two groups of archaic humans (hominins) were present at the site and the environmental conditions they faced before going extinct. The studies identify the age of the earliest Denisovans and Neanderthals in Southern Siberia. One of the studies, was led by Dr Katerina Douka from the Max Planck Institute for the Science of Human History, while the other one was led by Zenobia Jacobs of the University of Wollongong in Australia.
Over the course of five years, Dr Katerina Douka, Group Leader at the Max Planck Institute for the Science of Human History, and Professor Tom Higham, Director of the Oxford Radiocarbon Accelerator Unit at the University of Oxford, UK, have worked in close collaboration with a multi-disciplinary team from Russia, Australia, the United Kingdom, Canada and Germany on the detailed dating of the archaeological site of Denisova cave, in the foothills of Siberia’s Altai Mountains, the only site in the world known to have been occupied by both Neanderthals, Denisovans, and later by modern humans.
First direct proof for the interbreeding of Neanderthals and Denisovans
Excavations for the past 40 years led by archaeologists from the Institute of Archaeology and Ethnography (Siberian Branch of the Russian Academy of Sciences) in Novosibirsk, revealed the longest archaeological sequence in northern Eurasia. Denisova Cave first came to worldwide attention in 2010, when scientists from the Max Planck Institute for Evolutionary Anthropology obtained the genome from a fingerbone of a girl belonging to a group of humans not previously identified in the palaeoanthropological record – the Denisovans.
Based on analysis of the few and fragmentary hominin remains in the cave, further revelations followed on the genetic history of Denisovans and Altai Neanderthals. Last year, a bone fragment from Denisova Cave discovered by Samantha Brown, doctoral candidate in the Department of Archaeology at the Max Planck Institute for the Science of Human History, was genetically identified as the daughter of Neanderthal and Denisovan parents –the first direct evidence of interbreeding between two archaic hominin groups.
Innovative dating methods
However, reliable dates for the hominin fossils recovered from the cave have remained elusive, as have dates for the artefacts and animal remains retrieved from the sediments. More than 150 new dates are reported today in Nature, in two separate studies, providing a robust chronology for Denisova Cave. Fifty radiocarbon ages were obtained by Douka and her team on bone, tooth and charcoal fragments recovered from the upper layers of the site, while in a second study, led by Professor Zenobia Jacobs of the University of Wollongong in Australia, more than 100 optical ages were obtained for the cave sediments. A minimum age for the bone fragment of mixed Neanderthal/Denisovan ancestry was also obtained by uranium-series dating.
To determine the most probable ages of the archaic hominin fossils, Douka and her colleagues at Oxford developed a novel Bayesian model that combined several of these dates with information on the stratigraphy of the deposits as revealed by the Russian team, and genetic ages for the Denisovan and Neanderthal fossils relative to each other, the latter based on the number of substitutions in the mitochondrial DNA sequences calculated by Svante Pääbo’s team at the Max Planck Institute for Evolutionary Anthropology in Leipzig.
“This new chronology for Denisova Cave provides a timeline for the wealth of data generated by our Russian colleagues on the archaeological and environmental history of the cave over the past three glacial–interglacial cycles,” said lead author of the optical dating study, Professor Jacobs.
100,000 years ago, Neanderthals and Denisovans mingled here
The new studies show that the cave was occupied by Denisovans from at least 200,000 years ago, with stone tools in the deepest deposits suggesting human occupation may have begun as early as 300,000 years ago. Neanderthals visited the site between 200,000 and 100,000 years ago, with “Denny”, the girl of mixed ancestry, revealing that the two groups of hominins met and interbred around 100,000 years ago.
Most of the evidence for Neanderthals at Denisova Cave falls within the last interglacial period around 120,000 years ago, when the climate was relatively warm, whereas Denisovans survived through much colder periods, too, before disappearing around 50,000 years ago.
Modern humans were present in other parts of Asia by this time, but the nature of any encounters between them and Denisovans remains open to speculation in the absence of any fossil or genetic traces of modern humans at the site.
Oldest known artifacts from Northern Europe that are associated with modern humans
Douka’s team also identified the earliest evidence thus far in northern Eurasia for the appearance of bone points and pendants made of animal teeth that are usually associated with modern humans and signal the start of the Upper Palaeolithic. These date to between 43,000 and 49,000 years ago.
Professor Higham commented that “it is an open question as to whether Denisovans or modern humans made these personal ornaments found in the cave. We are hoping that in due course the application of sediment DNA analysis and further direct dating of such ornaments might enable us to identify the makers of these items, which are often associated with symbolic and more complex behaviour in the archaeological record.”