Homo Sapiens: Anatomically Modern Humans (AMH) Jan 28, 2019 23:44:09 GMT
Post by Admin on Jan 28, 2019 23:44:09 GMT
Over the past 30 years, understanding of Homo sapiens evolution has advanced greatly. Most research has supported the theory that modern humans had originated in Africa by about 200,000 years ago, but the latest findings reveal more complexity than anticipated. They confirm interbreeding between H. sapiens and other hominin species, provide evidence for H. sapiens in Morocco as early as 300,000 years ago, and reveal a seemingly incremental evolution of H. sapiens cranial shape. Although the cumulative evidence still suggests that all modern humans are descended from African H. sapiens populations that replaced local populations of archaic humans, models of modern human origins must now include substantial interactions with those populations before they went extinct. These recent findings illustrate why researchers must remain open to challenging the prevailing theories of modern human origins.
At an archaeological site near the Atlantic coast, finds of skull, face and jaw bones identified as being from early members of our species have been dated to about 315,000 years ago. That indicates H. sapiens appeared more than 100,000 years earlier than thought: most researchers have placed the origins of our species in East Africa about 200,000 years ago.
“Until now, the common wisdom was that our species emerged probably rather quickly somewhere in a ‘Garden of Eden’ that was located most likely in sub-Saharan Africa,” says Jean-Jacques Hublin, an author of the study and a director at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. Now, “I would say the Garden of Eden in Africa is probably Africa — and it’s a big, big garden.” Hublin was one of the leaders of the decade-long excavation at the Moroccan site, called Jebel Irhoud.
The re-dating and the tranche of new human bones convince Hublin that early H. sapiens once lived at Jebel Irhoud. “It’s a face you could cross in the street today,” he says. The teeth — although big compared with those of today's humans — are a better match to H. sapiens than they are to Neanderthals or other archaic humans. And the Jebel Irhoud skulls, elongated compared with those of later H. sapiens, suggest that these individuals' brains were organized differently.
This offers clues about the evolution of the H. sapiens lineage into today’s anatomically modern humans. Hublin suggests that anatomically modern humans may have acquired their characteristic faces before changes to the shape of their brains occurred. Moreover, the mix of features seen in the Jebel Irhoud remains and other H. sapiens-like fossils from elsewhere in Africa point to a diverse genesis for our species, and raises doubt about an exclusively East African origin.
“Homo sapiens, despite being so well known, was a species without a past until now,” says María Martínon-Torres, a palaeoanthropologist at University College London, noting the scarcity of fossils linked to human origins in Africa. But the lack of features that, she says, define our species — such as a prominent chin and forehead — convince her that the Jebel Irhoud remains should not be considered H. sapiens.
Chris Stringer, a palaeoanthropologist at the Natural History Museum in London, who co-authored a News & Views article accompanying the studies, says he was baffled by the Jebel Irhoud remains when he first saw them in the early 1970s. He knew that they weren’t Neanderthals, but they seemed too young and primitive-looking to be H. sapiens. But with the older dates and the new bones, Stringer agrees that the Jebel Irhoud bones stand firmly on the H. sapiens lineage. “They shift Morocco from a supposed backwater in the evolution of our species to a prominent position,” he adds.