origin of humans; Denisovan Neanderthal mixing (Origins)

by David Turell , Friday, July 19, 2024, 17:36 (50 days ago) @ David Turell

More DNA from the cave:

https://www.sciencemagazinedigital.org/sciencemagazine/library/item/19_july_2024/420769...

“'I’m pleased to tell you about a new Denisovan genome from a 200,000-year-old male,” said Peyrégne, a postdoc at the Max Planck Institute for Evolutionary Anthropology.

"The genetic sequence he unveiled is the oldest high-quality human genome yet—80,000 years older than the previous record holder, a Neanderthal who lived about 120,000 years ago. The results come after more than a decade of effort to find fossilized bones and a second genome of a Denisovan, the mysterious archaic human discovered through its DNA 14 years ago.

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"The genomes of both Denisovans and the ancient Neanderthal all came from the same cold, fossil-rich site: Denisova Cave in the Altai Mountains of Siberia.

According to the analysis by Peyrégne and colleagues, the newly sequenced male represents a distinct population of early Denisovans that interbred multiple times with a group of Neanderthals whose population had not been detected in DNA before.

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"Denisovans are primarily known from their DNA. Researchers have the genome of the girl, as well as bits of nuclear and mitochondrial DNA from fragmentary fossils of seven additional individuals, all also from Denisova Cave. Scientists have also identified some Denisovan DNA in living humans, including in Papuans and Han Chinese people, acquired from past interbreeding. DNA in sediments showed that Denisovans were first in the cave 300,000 years ago, and later lived in a cave on the Tibetan Plateau. The scanty fossils—teeth, a toe bone, a rib—reveal this archaic human had larger molars than did the Neanderthals and a robust lower face, known from a jawbone in China. But no one really knows what Denisovans looked like.

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"The DNA analysis revealed the male Denisovan had inherited 5% of his genome from an ancient, previously unknown population of Neanderthals. The male, labeled Denisova 25, came from a separate population of Denisovans from the girl, known as Denisova 3, and from the other Denisovans in the cave. The girl’s DNA is more closely related to the Denisovan sequences in living modern humans, who got them from at least two Denisovan populations.

"All this suggests the older male’s population was replaced in the cave by later Denisovans, Peyrégne said in his talk. The data also suggest the male Denisovan’s ancestors interbred multiple times with Neanderthals. Denisovans were apparently replaced in the cave by Neanderthals for a period, based on the Neanderthal fossil dated to about 120,000 years ago. By about 60,000 years ago, though, the Denisovans had moved back in. The two groups may even have met in the cave—DNA from a bone fragment from a female dated to more than 50,000 years ago shows her mother was a Neanderthal and her father a Denisovan. Later, both DNA and fossils indicate modern humans occupied the cave and Denisovans and Neanderthals disappear. The region was clearly a crossroads for various types of humans, Peyrégne said in the talk.

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"Although Denisovans and Neanderthals apparently interbred repeatedly, their lineages are distinct: They diverged from a common ancestor at least 400,000 years ago. The ancestors of Neanderthals settled in Europe and the Middle East, whereas Denisovans headed farther east into Asia where they evolved separately, acquiring roughly 300,000 genetic changes that differentiate them from Neanderthals, according to the new genome. “Neanderthals and Denisovans remain in separate groups,” and mixed at the edges of their geographic ranges, Peyrégne said in his talk.

"In the question and answer period, an audience member asked whether the male’s genome also had DNA from an even older, unidentified type of human—perhaps Homo erectus—whose DNA has been spotted in the Denisovan girl’s genome. “If there is any Denisova superarchaic ancestry, it’s also present in this genome,” Peyrégne responded. “[That DNA] is shared between Denisova 3 and Denisova 25.'” (my bold)

Comment: Note the bold. It is the first evidence of Erectus to Homo as a direct connection, which would indicate Bechly's point that all the other Homo sapiens fossils found are just variations of early sapiens. That the Denisovans and Neanderthals co-habituated means to me they were so similar, they easily lived together.