Scientists have extracted and analyzed DNA from three individuals of anatomically modern humans who lived between 45,930 and 42,580 years ago in what is now Bulgaria.
“Modern humans appeared in Europe by at least 45,000 years ago, but the extent of their interactions with Neanderthals, who disappeared by about 40,000 years ago, and their relationship to the broader expansion of modern humans outside Africa are poorly understood,” said co-lead author Dr. Mateja Hajdinjak, a researcher in the Department of Evolutionary Genetics at the Max Planck Institute for Evolutionary Anthropology and Francis Crick Institute, and his colleagues.
“Analyses of the genomes of Neanderthals and modern humans have shown that gene flow occurred between the two hominin groups approximately 60,000-50,000 years ago, probably in southwestern Asia.”
“However, owing to the scarcity of modern human remains from Eurasia that are older than 40,000 years, genome-wide data are available for only three individuals of this age. Little is therefore known about the genetics of the earliest modern humans in Eurasia, the extent to which they interacted with archaic humans and their contribution to later populations.”
“For example, whereas 42,000 to 37,000-year-old ‘Oase1’ individual from Romania and 45,000-year-old ‘Ust’Ishim’ individual from Siberia do not show specific genetic relationships to subsequent Eurasian populations, 40,000-year-old ‘Tianyuan’ individual from China contributed to the genetic ancestry of ancient and present-day East Asian populations.”
“Another open question is the extent to which modern humans mixed with Neanderthals when they spread across Europe and Asia.”
In the new study, the researchers sequenced the genomes from the modern human remains dated to between 45,930 and 42,580 years ago.
The specimens were found in direct association with an assemblage of artifacts in Bacho Kiro Cave, Bulgaria.
“They are the earliest Late Pleistocene modern humans known to have been recovered in Europe so far, and were found in association with an Initial Upper Paleolithic artifact assemblage,” the scientists said.
Unlike two previously studied Oase1 and Ust’Ishim individuals who did not contribute detectably to later populations, the Bacho Kiro individuals are more closely related to present-day and ancient populations in East Asia and the Americas than to later west Eurasian populations.
Moreover, the authors found that all three individuals had Neanderthal ancestors a few generations back in their family history.
This suggests that mixing between Neanderthals and the first modern humans that arrived into Europe was perhaps more common than is often assumed.
“We found that the Bacho Kiro Cave individuals had higher levels of Neanderthal ancestry than nearly all other early humans, with the exception of ‘Oase1’ individual from Romania,” Dr. Hajdinjak said.
“Crucially, most of this Neanderthal DNA comes in extremely long stretches. This shows that these individuals had Neanderthal ancestors some five to seven generations back in their family trees.”
“The results suggest that the first modern humans that arrived in Eurasia mixed frequently with Neanderthals,” added senior author Professor Svante Pääbo, a researcher in the Department of Evolutionary Genetics at the Max Planck Institute for Evolutionary Anthropology.
“They may even have become absorbed into resident Neanderthal populations. Only later on did larger modern human groups arrive and replace the Neanderthals.”
The findings were published in the journal Nature.
M. Hajdinjak et al. 2021. Initial Upper Palaeolithic humans in Europe had recent Neanderthal ancestry. Nature 592, 253-257; doi: 10.1038/s41586-021-03335-3