origin of humans; neanderthal sapiens breeding brief (Origins)

by David Turell , Tuesday, May 28, 2024, 23:33 (177 days ago) @ David Turell

At a period about 47.000 years ago:

https://www.nature.com/articles/d41586-024-01452-3?utm_source=Live+Audience&utm_cam...

"...a study of hundreds of ancient and modern genomes has pinpointed when the two species began pairing off — and has found that the genetic intermingling lasted for only a short time, at least on an evolutionary scale.

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"Earlier studies tried to understand this history by comparing contemporary human genomes with a small number of Neanderthal ones. But this approach makes it challenging for researchers to define where Neanderthal sequences in the modern genome start and end.

"To address this challenge, Leonardo Iasi, an evolutionary geneticist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and his colleagues analysed 58 individuals who lived between 2,200 and 45,000 years ago and compared their DNA with that of 231 modern individuals of diverse ancestries other than African ones. People of full African ancestry don’t carry substantial amounts of Neanderthal DNA because their forebears were not part of the exodus from the continent while Neanderthals were alive.

"This large-scale, multi-millennia-spanning comparison made it more straightforward to monitor ‘introgression’ of Neanderthal-derived sequences into the modern human genome. The results indicated that Neanderthal-derived genetic contributions in the modern samples could be traced to a single ‘pulse’ of gene flow starting roughly 47,000 years ago — more recently than originally projected —and spanning some 6,800 years, ending around the same time that Neanderthals were nearing extinction. Nearly 7,000 years might seem like a long time, but it is remarkably short on evolutionary timescales considering the sizable changes that the human genome underwent.

"Notably, many of the Neanderthals’ genomic contributions were subsequently removed with remarkable speed from the H. sapiens genome. Modern human genomes contain vast ‘deserts’ that have been fully cleared of Neanderthal remnants — but the authors detected these deserts even in ancient genomes from the latest stages of human–Neanderthal interaction. According to Emilia Huerta-Sanchez, an evolutionary biologist at Brown University in Providence, Rhode Island, this suggests that many Neanderthal sequences could have been detrimental to humans, and were therefore actively and rapidly selected against by evolution.

"Huerta-Sanchez says this work fills important gaps in ancient human history. “One of the strengths of the study is that by incorporating ancient human genomes, they learnt more about how evolutionary forces have shaped Neanderthal variation in human populations,” she says.

"But other gaps remain. For example, ancestral human genomic data from some geographical regions, including Oceania and East Asia, are much scarcer than from western Eurasia. East Asia is particularly intriguing, because modern humans in the region retain especially high levels of Neanderthal DNA — roughly 20% more than do European people."

Comment: the interbreeding had to be fast and furious but seeing different females is always tempting to the male. A designer would not have to help.