Evolution and humans:H. sapiens 350,000 years ago (Evolution)

by David Turell @, Wednesday, June 07, 2017, 19:49 (499 days ago) @ David Turell

Another article on this new human find which differs in the description and conclusions:

https://www.newscientist.com/article/2133807-our-species-may-be-150000-years-older-than...

Has our species been hiding its real age? Fossils found in Morocco suggest the Homo sapiens lineage became distinct as early as 350,000 years ago – adding as much as 150,000 years to our species’ history.

On a literal reading of the fossil record, H. sapiens was thought to have emerged in East Africa roughly 200,000 years ago. But some researchers have long suspected that the roots of our species are deeper, given that H. sapiens-like fossils in South Africa have been tentatively dated at 260,000 years old.

The new evidence provides solid support to those suspicions. It comes from a Moroccan site called Jebel Irhoud (pictured below), which has been puzzling human evolution researchers for more than 50 years.

Hominin remains were found at the site in the 1960s. They have such an odd mix of ancient and modern features that they were initially mistaken for an African version of Neanderthals. Later reassessments put them closer to our species, and about a decade ago a dating technique suggested they were about 160,000 years old.

But by that point in prehistory, it is conventionally assumed that our fully modern species were already living in Africa, which made the Jebel Irhoud hominins’ mix of ancient and modern features confusing.

An analysis of the new fossils, and of those found at the site in the 1960s, confirms that the hominins had a primitive, elongated braincase. But the new adult skull shows that the hominins combined this ancient feature with a small, lightly built “modern” face – one that the researchers say is virtually indistinguishable from H. sapiens.

By assessing the levels of radiation at the site and measuring the radiation response in the tools, McPherron and his colleagues established that the tools were heated between 280,000 and 350,000 years ago. McPherron’s team also re-dated one of the hominin fossils found in the 1960s using their insight into the radiation levels at Jebel Irhoud and concluded it is 250,000 to 320,000 years old.

Armed with these dates, the Moroccan hominins become easier to understand, says Hublin. The researchers suggest that H. sapiens had begun to emerge – literally face-first – between about 250,000 and 350,000 years ago. Although other features of their anatomy still looked primitive, the Jebel Irhoud hominins should be considered the earliest known members of our species, say Hublin and his colleagues.

“The face is modern looking,” says Juan Luis Arsuaga at the Complutense University of Madrid, Spain. “But the mandible [jawbone] is not clearly modern. I would say that Jebel Irhoud is not yet H. sapiens, but I would bet that H. sapiens evolved from something very similar to Jebel Irhoud.”

However, Chris Stringer at the Natural History Museum in London is willing to loosen the definition of H. sapiens. ... We should consider including the Moroccan hominins in our species even though some of their features look ancient, he says.

Stringer thinks we shouldn’t be surprised to discover that our species is far more ancient than once thought. We know that our lineage split from the Neanderthal lineage at some point in prehistory, with Neanderthals then evolving in Europe while H. sapiens evolved in Africa. Recently, fossil and genetic evidence has suggested that this split occurred at least 500,000 years ago. “In my view, the date of this divergence should mark the origin of these two groups,” says Stringer.

This would imply that, roughly 500,000 years ago, Neanderthal-like hominins began appearing in Europe and H. sapiens-like hominins began appearing in Africa. In keeping with this idea, 430,000-year-old hominins found at a site called Sima de los Huesos in Spain do seem to be Neanderthal-like. But although the Jebel Irhoud fossils suggest H. sapiens had evolved a modern face 350,000 years ago, working out how, where and when our species evolved its other modern features will be challenging. “We have so few well-dated fossils,” says McPherron.

Comment: this ranch appears to be possibly a pre-branch before more modern H. sapiens appeared?


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