Neanderthals likely began 'mixing' with modern humans later than previously thought

Scientists have pinpointed a time frame in which Neanderthals began "mixing" with modern humans, based on the DNA of early inhabitants of Europe.

Analysis of the oldest-known genomes from early modern humans who lived in Europe indicates that the mixing occurred more recently than previous estimates, according to a paper published in Nature on Thursday.

The mixing likely occurred between 45,000 and 49,000 years ago -- meaning the two genetically distinct groups overlapped on the European continent for at least 5,000 years, according to the paper.

Radiocarbon dating of bone fragments from Ranis, Germany, were shown to have 2.9% Neanderthal ancestry, which the authors believe occurred from a single mixing event common among all non-African individuals.

The mixing event likely occurred about 80 generations before those individuals lived, the researchers said.

The group from Ranis also represents the oldest-known family units, Arev Sumer, a researcher at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and co-author of the paper, said during a news conference on Wednesday. Six individuals from the group were found to have a close kinship, including a mother and daughter.

The findings imply that the ancestors of all currently sequenced non-African early humans lived in a common population during this time, stretching from modern Great Britain to Poland, Johannes Krause, a biochemist at the Max Planck Institute for Evolutionary Anthropology and co-author of the study, said during the news conference.

"This was rather surprising, because modern humans had just left Africa a few thousand years earlier and had reached this northern part of Europe where climatic conditions were rather cold -- much colder than today," Krause said. "It was the middle of the Ice Age."

Groups of early humans previously studied in Europe showed very few cases of mixing between Neanderthals and Homo sapiens, according to the paper.

The groups were represented by individuals from the Bacho Kiro region in Bulgaria and a woman named Zlaty kun from Czechia -- believed to be part of the earliest population to diverge from the "Out-of-Africa" lineage, a small group of Homo sapiens that left the African continent about 80,000 years ago.

Within those two groups, the individuals from Bulgaria only suggest two mixing events with Neanderthals, while Zlaty kun's lineage only suggests one mixing event, according to the paper.

Zlaty kun was found to have a fifth- or sixth-degree genetic relationship with two Ranis individuals, Sumer said, adding that the Ranis group was part of a small population that left no descendants among present-day people.

Neanderthals are believed to have become extinct about 40,000 years ago, Krause said.

The findings offer researchers a much more precise window of time in which the mixing occurred, as well as more insights into the demographics of early modern humans and the earliest Out-of-Africa migrations, according to the paper.

More research is needed to explore the events following the Out-of-Africa migration and the earliest movements of modern humans across Europe and Asia, Sumer said.

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