Evolution and humans: all over Africa (Evolution)

by David Turell @, Thursday, April 26, 2018, 21:39 (950 days ago) @ dhw

As more and more human fossils turn up, as judged by the shape of the skull, advanced an more archaic forms from the same time periods are popping up all over the place in Africa and Asia. The earliest human is 315,000 years old:


"In fact, if you were to travel back to the very beginnings of our species and select a random group of humans, they would look unlike anyone living today in Africa or elsewhere. What’s more, they would show extraordinary physical variation – greatly exceeding that in modern human populations. Far from becoming more diverse as we have adapted to life in different parts of the planet, Homo sapiens is more homogeneous today than our ancestors were.

"This is a real puzzle. It simply doesn’t fit with the long-held idea that we arose from a single population in a corner of East Africa. In fact, mounting evidence from fossils, archaeological remains and genetic analysis points in a new direction. Now researchers, including myself, are trying to work out what it all means: why our African forebears were so physically different from each other, and how our species lost the huge variety it once had.


"Humans alive today have a characteristic skull shape, including a rounded braincase, a smooth, high forehead, a small face and a prominent chin. However, these features don’t appear all together in any early member of our species. Instead, we see a wide variety of skulls that exhibit different mixes of modern features alongside archaic ones, such as large, robust faces, pronounced brow ridges and elongated braincases. This fuelled disagreements about which constellation of features should be used to distinguish early members of our species from now-extinct hominins.


"The ability to create and combine items that don’t occur together in nature in anticipation of a range of diverse tasks has long been seen as a reflection of advanced cognition. It is considered a hallmark of our species. But here’s the thing: abundant evidence makes it increasingly clear that the Middle Stone Age didn’t emerge in one location at the purported dawn of humanity. Instead, there was a wholesale, continent-wide shift to this new technology around 300,000 years ago.


"Perhaps other hominin species were living in Africa alongside us for far longer than anyone imagined. Alternatively, these strange-looking beings were humans, raising the possibility that some pre-200,000-year-old fossils with equally bizarre looks might also belong to our species. The idea that we should cast our net more widely when fishing for early humans gains support from another quarter. Advances in genetic analysis have revealed the first glimmerings of an older origin for H. sapiens, with the discovery that we and our sister species, the Neanderthals, shared a last common ancestor about half a million years ago. Such developments have led some to question the classification of a diverse array of early fossils from across Africa.

"Then, last year, came the discovery of new early H. sapiens fossils. They didn’t come from East Africa, nor were they less than 200,000 years old. Instead, they dated to a staggering 315,000 years ago and were found in the far north-west of the continent, in Morocco. “This find changes everything,” says Philipp Gunz of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, who analysed the fossils. “These early individuals had modern faces and modern teeth, but elongated braincases. This suggests that features of brain shape, and perhaps even brain function, emerged within our species.”


" In an upcoming paper, we suggest that a diverse array of H. sapiens populations, displaying a mosaic of archaic and modern features, lived over an extensive geographic area from Morocco to South Africa between about 300,000 and 12,000 years ago.


"Instead, a messy beginning involving multiple populations, regions and environments is in. Although this scenario is more complex, it reconciles the genetic, fossil and archaeological evidence. It also explains the early, pan-African emergence of the Middle Stone Age as an outcome of becoming human.


"We know that 12,000 years ago marks the beginning of a revolution for humanity. This is when Earth’s climate entered a warm and unusually stable period known as the Holocene, which persists to this day. It seems likely that people have always tried to control and alter their environment, but with climatic stability such experiments were finally able to take off. Farming was born. And this had big implications for human evolution.


"The homogenising effect on humanity was so pronounced that anthropologist Marta MirazÓn Lahr at the University of Cambridge has dubbed it the “Holocene filter”.

"Yet the truly astonishing revelation is that we were so diverse in the first place. As this new narrative is fleshed out, there are bound to be more surprises. "

Comment: During the past 12,000 years we really learned how to use our brains. We had been partially civilized; we had farmed food and lived above a survival existence which allowed us to really start thinking.

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