Human evolution: a fossil with unknown DNA (Introduction)

by David Turell , Sunday, November 27, 2022, 16:43 (508 days ago) @ David Turell

A female from a Siberian cave, about 50,000 years ago:

https://www.sciencealert.com/an-ai-found-an-unknown-ghost-ancestor-in-the-human-genome?...

"Nobody knows who she was, just that she was different: A teenage girl from over 50,000 years ago of such odd uniqueness she appeared to be a 'hybrid' ancestor to modern humans that scientists hadn't seen before.

"Only recently, researchers have uncovered evidence she wasn't alone. In a 2019 study analyzing the tangled mess of humanity's prehistory, scientists used artificial intelligence (AI) to identify an unknown human ancestor species that modern humans encountered – and shared dalliances with – on the long trek out of Africa millennia ago.

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"Up until recently, these occasional sexual partners were thought to include Neanderthals and Denisovans, the latter of which were unknown until 2010.

"But in this study, a third ex from long ago was isolated in Eurasian DNA, thanks to deep learning algorithms sifting through a complex mass of ancient and modern human genetic code.

"Using a statistical technique called Bayesian inference, the researchers found evidence of what they call a "third introgression" – a 'ghost' archaic population that modern humans interbred with during the African exodus.

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"Also in 2018, another team of researchers identified evidence of what they called a "definite third interbreeding event" alongside Denisovans and Neanderthals, and a pair of papers published in early 2019 traced the timeline of how those extinct species intersected and interbred in clearer detail than ever before.

"There's a lot more research to be done here yet. Applying this kind of AI analysis is a decidedly new technique in the field of human ancestry, and the known fossil evidence we're dealing with is amazingly scant.

"But according to the research, what the team has found explains not only a long-forgotten process of introgression – it's a dalliance that, in its own way, informs part of who we are today.

"'We thought we'd try to find these places of high divergence in the genome, see which are Neanderthal and which are Denisovan, and then see whether these explain the whole picture," Bertranpetit told Smithsonian.

"'As it happens, if you subtract the Neanderthal and Denisovan parts, there is still something in the genome that is highly divergent.'"

Comment: We have discussed before the large bush of homo forms that preceded the final arrival of H. sapiens. What seems to be a pattern is when a type of animal appears it spreads out into many species, as dinosaurs, whales, birds, etc. show. But in this case only one remains after a burst of forms. Chance or guided by God?