Two groups of archaic humans — Neanderthals and their enigmatic cousins, Denisovans — occupied Denisova Cave in the Altai region of Siberia almost continuously through relatively warm and cold periods over the past 200,000 years, according to two new studies published in the January 31, 2019 issue of the journal Nature: fossils and DNA traces of Denisovans are found from at least 200,000 to 50,000 years ago, and those of Neanderthals between 200,000 and 100,000 years ago. In 2018, a bone fragment from the cave yielded the genome of the daughter of Neanderthal and Denisovan parents. The new studies reveal that this girl lived around 100,000 years ago.
Neanderthals in a cave. Image credit: Tyler B. Tretsven.
The Altai region of Siberia was inhabited for parts of the Pleistocene by at least two archaic human (hominin) groups: Denisovans and Neanderthals.
Denisova Cave is a key site for understanding the complex relationships between these groups as it contains deposits that preserve skeletal and genetic evidence of both hominins, artifacts made from stone and other materials, and a range of animal and plant remains.
The cave is situated in the foothills of the Altai Mountains and has been excavated for the past four decades by archaeologists from the Institute of Archaeology and Ethnography in Novosibirsk.
The site first came to worldwide attention in 2010, with the publication of the genome obtained from the fingerbone of a girl belonging to a group of humans not previously identified in the paleoanthropological record, the Denisovans.
Further revelations followed on the genetic history of Denisovans and Altai Neanderthals, based on analysis of the few and fragmentary hominin remains.
Last year, a bone fragment from the cave yielded the genome of the daughter of Neanderthal and Denisovan parents — the first direct evidence of interbreeding between two hominin groups.
Until now, reliable dates for the hominin fossils recovered from the cave deposits remained elusive, as did dates for the DNA, artifacts, and animal and plant remains retrieved from the sediments.
Denisova Cave in the Altai Mountains of southern Siberia. Image credit: Alex Demin / CC BY-SA 4.0.
More than 100 optical dating ages and 50 radiocarbon dating ages support the new chronology for Denisova Cave, as well as a minimum age for the bone fragment of mixed Neanderthal/Denisovan ancestry obtained by uranium-series dating.
One of the two new studies, led by University of Wollongong’s Professor Zenobia Jacobs, involved optical dating of the cave sediments, most of which are too old for radiocarbon dating.
The other study, led by Dr. Katerina Douka from the Max Planck Institute for the Science of Human History, obtained radiocarbon ages from bone, tooth and charcoal fragments recovered from the upper layers of the site, and developed a statistical model to integrate all dating information for the cave.
“This new chronology for Denisova Cave provides a timeline for the wealth of data generated by our colleagues in Siberia on the archaeological and environmental history of the cave over the past three glacial-interglacial cycles,” Professor Jacobs said.
“We had to invent some new methods to date the deepest and oldest deposits and construct a robust chronology for the sediments in Denisova Cave,” said University of Wollongong’s Dr. Bo Li.
“The improved age estimates for the hominin fossils obtained using the novel Bayesian age model, incorporate all of the dating evidence available for these small and isolated fossils, which can sometimes be displaced after deposition in a cave sequence,” Dr. Douka said.
Artifacts from Denisova Cave: (a) Upper Paleolithic artifacts – (1-3) bladelets, (4) retouched blade, and (5) end-scraper; (b) Initial Upper Paleolithic artifacts – (1) marble ring, (2) tubular beads, (3) ivory pendant, (4) pendant made of red deer tooth, (5) ivory ring, (6) pendant made of elk tooth, (7) chloritolite bracelet, (8) bone needle, (9) end-scraper, (10) retouched point, (11) biface, and (12) pointed blade; (c) artifacts of middle Middle Paleolithic assemblage – (1) blade, (2) and (5) Mousterian points, (3) Levallois point, and (4) scraper; (d) Early Middle Paleolithic assemblage – (1) core, (2) and (4) scrapers, (3) denticulate tool. Image credit: Jacobs et al, doi: 10.1038/s41586-018-0870-z.
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 50,000 years ago, 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.
“For the same reason, another open question is whether Denisovans or modern humans made the oldest bone points and personal ornaments (tooth pendants) found in the cave,” said University of Oxford’s Professor Tom Higham.
“With direct dates of between 43,000 and 49,000 years ago, they are the earliest such artifacts known from all of northern Eurasia.”
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Zenobia Jacobs et al. 2019. Timing of archaic hominin occupation of Denisova Cave in southern Siberia. Nature 565: 594-599; doi: 10.1038/s41586-018-0843-2
Katerina Douka et al. 2019. Age estimates for hominin fossils and the onset of the Upper Palaeolithic at Denisova Cave. Nature 565: 640-644; doi: 10.1038/s41586-018-0870-z
Source link: https://www.sci.news/archaeology/denisovans-neanderthals-denisova-cave-06864.html
