Human evolution: more on Morocco fossils from 315,000 ya (Introduction)

by David Turell , Tuesday, October 29, 2024, 15:59 (23 days ago) @ David Turell

From ~315,000 years ago:

https://www.nationalgeographic.com/history/article/morocco-early-human-fossils-anthropo...

"Now, examinations of fire-baked tools from the site suggest that these ancient people lived more than 300,000 years ago, making them twice as old as previously thought.

"The findings, announced in Nature on Wednesday, fill a crucial gap in the human fossil record. That’s because these people bear many striking similarities to modern humans even though they lived well before what may be the oldest fossil evidence of Homo sapiens, from a site in Ethiopia dated to about 195,000 years ago.

"The residents of the Moroccan site weren’t quite the Homo sapiens of today; their skulls were less rounded and more elongated than ours, perhaps signaling differences between our brains and theirs. However, their teeth closely resemble those in the mouths of modern humans—and their faces looked just like ours.

***

"What’s more, the Moroccan site is in northwest Africa, far from the sites in East and South Africa that have yielded many of Africa’s other hominin fossils.

"To paleoanthropologists, the combination of this site’s age and location serve as a powerful reminder that the evolution of modern humans was likely more ancient, and more dispersed across Africa, than previous discoveries suggested.

***

"The Moroccan site, known as Jebel Irhoud, was an active barite mine when it first made scientific waves in the 1960s. Digging yielded stone tools and some enigmatic skull fragments, which scientists initially assigned to an ancient relative of modern humans.

***

"To researchers’ delight, a piece of the archaeological site survived under the mining rubble—and it yielded more stone tools, ample evidence of humans using fire, and some skeletal remains, including a lower jaw and part of a braincase.

"Importantly, finding the stone tools and skeletal remains in the same rock layer meant that Hublin’s team could use the tools to more accurately date the Jebel Irhoud fossils.

"The team took advantage of the fact that the stone tools had been scattered around and inadvertently heated by the Jebel Irhoud humans’ campfires. Heating the stone tools zeroed out the electrical charge they had been carrying. That means any charge in the tools today would have been generated after they were buried, as the surrounding sediments bombarded the stone with natural radioactivity.

"Hublin’s team spent a year measuring the radioactivity of the Jebel Irhoud site. By comparing this annual radiation dose to the tools’ current electrical charge, the team determined that the Jebel Irhoud campfires baked the tools about 315,000 years ago, give or take 34,000 years. (my bold)

***

"Jebel Irhoud’s dates overlap with the dates recently ascribed to Homo naledi, an extinct—and anatomically bizarre—hominin species discovered in South Africa. The find provides further evidence that at least two dramatically different species of hominins occupied Africa at the same time.

"Given the Jebel Irhoud fossils’ modern faces and primitive braincases, Hublin and his team suggest that the features associated with modern humans probably didn’t evolve all at once. Instead, various traits we associate with anatomically modern humans probably appeared in a type of “mosaic evolution” that Neanderthals also seem to have exhibited.

"Modern humankind “wasn’t a new model of an automobile that appeared in a showroom with all the bells and whistles,” says Wood. “Different parts of modern human morphology and behavior probably came incrementally.”

"The find also shows how the precursors to modern humans could have dispersed widely across Africa, Hublin’s team says. For instance, perhaps they spread into northern Africa during periodic “green Sahara” events, when the forbidding desert sometimes gave way to more hospitable grassland.

"However, Hublin and his coauthor Shannon McPherron emphasize that they cannot yet say precisely where modern humans evolved on the continent.

"In addition, the finds present an intriguing dilemma: Should paleoanthropologists treat the Jebel Irhoud remains as part of the Homo sapiens species?

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"While Hawks applauds the researchers for their careful re-excavations, he also cautions against overplaying the papers’ significance.

“Many scientists have noted the very archaic features of the [Jebel Irhoud] braincase, and some more similarities with modern humans in the face,” he adds by email. Hublin and his colleagues “really aren’t adding anything new except the date.”

"For Wood, though, Hublin’s use of “early modern humans” makes sense. And regardless of precise labels, he says, the Jebel Irhoud fossils have their place in the tapestry of humankind.

“'Three hundred thousand years ago, there is fossil evidence of a population that in a remarkable number of ways resembles modern humans, and you can make of that what you like,” says Wood.

“'You can either expand the definition of Homo sapiens to include [Jebel Irhoud], or these were creatures that were on their way to [becoming] modern humans.'”

Comment: An earlier report was presented here giving the 315,000 year's ago dating, with the statement the fossils were H sapiens. They certainly were 'almost' our level of development.