origin of humans; latest theories (Origins)

by David Turell , Tuesday, December 10, 2024, 18:36 (11 days ago) @ David Turell

a new story:

https://mail.google.com/mail/u/0/#inbox/FMfcgzQXKhDwtWPktwHdVfsJNwGDHLkC

“'What I want to single out as the biggest advance in the last five years is the shift to understanding that the origin of our genus, Homo, was not uniquely connected with stone tools and meat eating,” says John Hawks at the University of Wisconsin-Madison.

"According to Hawks, the “textbook picture” was that “stone tools, meat eating, taller stature, smaller molars and jawbones, and larger brains were all connected with each other, and all coincident with the origin of Homo”. On this view, the evolution of Homo “looked like a single quantum shift – a very tidy package”.

"However, multiple lines of evidence suggested otherwise, and Hawks says, “The work of the last five years has really triggered the advance in understanding.” For example, in 2023 researchers described the oldest known Oldowan stone tools from Nyayanga in Kenya. They are 2.6 million to 3 million years old and were found, not with Homo, but with teeth from Paranthropus: hominins with big teeth and small brains. Likewise, a study published in October found that early hominins called Australopithecus used their hands in similar ways to later Homo, perhaps making and using stone tools. Hawks also highlights a 2022 study that found no evidence of a sustained increase in meat eating after the evolution of Homo erectus.

"I will add one other data point. In late November, a study concluded that hominin brains became bigger gradually, with early members of a given species having smaller brains than later members of the same species. This was not a given: there had been claims that brain size jumped dramatically in the first Homo, as per the textbook “package” idea.

"This all makes for a more complicated story. But, says Hawks: “To me this is all exciting because it puts us in a position to test for cause and effect.” By following how different hominins behaved and evolved, it should be possible to see what caused what. For instance, did meat eating enable the growth of bigger brains, or did bigger brains enable more advanced hunting and thus more meat eating?

***

"The old idea that our species originated from a single place in Africa now looks unlikely, says Eleanor Scerri at the Max Planck Institute of Geoanthropology in Jena, Germany. She highlights a 2023 study of modern genetics, which suggests there were multiple H. sapiens populations in Africa for hundreds of thousands of years, linked by occasional interbreeding. That same year, evidence emerged of humans living in Senegal, in West Africa, far from our supposed origins in eastern or southern Africa, 150,000 years ago. “This was thrilling because it provides support for the view that humans evolved in multiple different ecoregions and parts of Africa,” says Scerri.

“'For me, it's the rewriting of the human origins story for Homo sapiens, specifically on ‘out of Africa’,” says Michael Petraglia at Griffith University in Australia. It used to be thought that H. sapiens came out of Africa in a “single, rapid coastal migration” about 60,000 years ago, but researchers now recognise multiple migrations beginning at least 200,000 years ago. “We also have on-the-ground evidence to indicate that migrations were terrestrial, not coastal,” says Petraglia. That migration at 60,000 years ago is still crucial, because most people living outside Africa are descended from those who came out at that time: the earlier migrations seem to have left few genetic traces in modern populations. But these migrations also matter.

***

“'For me perhaps the biggest advance of recent years has been a conceptual shift in our perspective away from the idea that early Homo sapiens were somehow on a trajectory of predestined success, leaving behind all the ‘evolutionary losers’,” says Rebecca Wragg Sykes at the University of Cambridge. “Instead, what we're seeing more and more is nuance in the story of early H. sapiens populations: from our complex African emergence, our numerous dispersals into Eurasia and interactions there, and the fact that it seems at least some of the pioneer sapiens populations themselves vanished.”

'"Finally, researchers have begun paying more attention to a group of humans they previously all but ignored: children. As with so much of human evolution, “it is all about relationships”, says Nowell. “Not studying children to any serious degree meant that we were ignoring the contributions and experiences of two-thirds of the human population for more than 99 per cent of our time on Earth.” Furthermore, “by ignoring their experiences, we were also not accounting for the experiences of others in their communities in relation to them'”.

Comment: our superiority as sapiens resulted in our success in becoming dominant. The dispersed Erectus became sapiens in several places in Africa seems obvious. We did not start like Adam and Eve.