Wednesday, July 17, 2019

Ancient DNA From Neanderthals In Gibraltar And A Very Old Archaic Modern Human Skull In Greece

Ancient mtDNA from two Neanderthals in Gibraltar at a site known as Forbes' Quarry helps shed light on Neanderthal population genetics and history as illustrated in Figure A.

Autosomal DNA analysis described in Figure B shows how much nuclear DNA these Neanderthals had in common with other hominins. Among other things, this shows that there was introgression from humans into Neanderthals as well as the other way around, and from Denisovans into Neanderthals.

A Very Old Skull With Modern Human Traits In Greece

In other Neanderthal news, a skull much older than any modern human skull previously found in Europe with modern human features has been found near a Neanderthal skull on the Mani Peninsula in the Peloponnese region of Greece. 

My take on the find is that it is less paradigm shaking that some of suggested and really just involves a modern human-Neanderthal hybrid individual who was raised in a Neanderthal community not very far from the point of first contact between modern humans and Neanderthals. I also wouldn't rule out the possibility that the dating of this skull, which relies on tricky methods and reasonable, but not infallible assumptions, could be wrong.

The Atlantic magazine explains the situation in a July 10, 2019 story:
In 1978, in a cave called Apidima at the southern end of Greece, a group of anthropologists found a pair of human-like skulls. One had a face, but was badly distorted; the other was just the left half of a braincase. Researchers guessed that they might be Neanderthals, or perhaps another ancient hominin. And since they were entombed together, in a block of stone no bigger than a microwave, “it was always assumed that they were the same [species] and came from the same time period,” says Katerina Harvati from Eberhard Karls University of Tübingen. . . .

“Apidima 1 has just been ignored,” says Harvati. But its antiquity matters for three reasons. First, it pushes back the known presence of modern humans outside Africa by some 30,000 years. Second, it’s considerably older than all other Homo sapiens fossils from Europe, all of which are 40,000 years old or younger. Third, it’s older than the Neanderthal skull next to it.

Collectively, these traits mess up the standard story of Neanderthal and modern-human evolution. According to that narrative, Neanderthals slowly evolved in Europe, largely isolated from other kinds of hominins. When modern humans expanded out of Africa, their movements into Europe might have been stalled by the presence of the already successful Neanderthals. That explains why Homo sapiens stuck to a more southerly route into Asia, and why they left no European fossils until about 40,000 years ago. “The idea of Europe as ‘fortress Neanderthal’ has been gaining ground,” says Rebecca Wragg Sykes, an archaeologist from the University of Bordeaux, but identifying a 210,000-year-old Homo sapiens skull from Europe “really undermines that.” . . .
These interpretations depend on the dating of the Apidima skulls, which has always been difficult. They were found in an odd place—a small niche near the cave ceiling, separated from any sediments that could have been easily dated. They were also entombed in breccia, a composite rock made from fragments that have been cemented together. It seems that, as ice ages came and went and sea levels rose and fell, parts of the cave’s interior were flooded and eroded, and both skulls were dislodged from their original resting places. They fell into a cavity and got stuck.

Harvati’s team estimated their ages by analyzing the minute amounts of uranium within them. They then scanned both skulls, reconstructed what they would have looked like before being broken and distorted, and compared their three-dimensional shapes with those of other hominins. In that comparison, Apidima 2 clearly clustered with Neanderthals, while Apidima 1 grouped with skulls from modern humans. . . .

Apidima 1 lacks several traits that are distinctively Neanderthal, while its rounded shape “is considered to be a uniquely modern human feature that evolved relatively late,” Harvati says.  But “it doesn’t look like classic Homo sapiens,” says Wragg Sykes, who wonders whether it represents a group of humans that had been interbreeding with Neanderthals or other ancient hominins. “Obviously everyone is going to want to see DNA out of that skull,” she adds. . . . 
Harvati thinks that modern humans were already in Greece about 200,000 years ago; they were then replaced by Neanderthals, who were themselves replaced by humans about 40,000 years ago. A similar cycle of competition, where Neanderthals and humans repeatedly replaced each other, seems to have happened in the Levant, the Middle Eastern region that includes Israel and Syria. “We can’t refer to Homo sapiens as a ‘success’ in terms of being able to move into new areas and stay there,” Wragg Sykes says.
Of course, it’s possible that both hominins just lived together. But genetic studies suggest that while they did intermittently meet and mate, the groups weren’t in constant contact. “I don’t think they coexisted,” says Harvati. “But maybe I’m wrong. We don’t have the evidence one way or the other, and we need to look for more.”
Harvati's theory that the boundary between modern humans and Neanderthals shifted back and forth over time and that there were was more than one round of advance and retreat by modern humans is also very plausible and not very paradigm shaking.

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