The fossilized remains of at least five individuals discovered at the archaeological site of Jebel Irhoud in Morocco have been dated at 315,000 years, making them the oldest known fossils of anatomically modern Homo sapiens. The discovery is described in two papers released today by the journal Nature.
Finds at the Middle Stone Age site of Jebel Irhoud, Morocco, reveal modern humans in northwest Africa 300,000 years ago. Image credit: Charles R. Knight.
Jebel Irhoud has been well known since the 1960s for its human fossils and for its Middle Stone Age artifacts, but the geological age of those fossils was uncertain.
The new excavation project uncovered 16 new Homo sapiens fossils along with stone tools and animal bones. The remains comprise skulls, teeth, and long bones of at least five individuals.
Thermoluminescence dating of heated flints yielded an age of approximately 315,000 years ago.
Analysis of the animal fossils provided additional evidence to support the date. Dating of rodent remains suggested they were 337,000 to 374,000 years old.
“The fossils revealed a complex evolutionary history of mankind that likely involved the entire African continent,” said co-author Professor Rainer Grün, of the Australian National University.
“The crania of modern humans living today are characterized by a combination of features that distinguish us from our fossil relatives and ancestors — a small and gracile face, and globular braincase,” the researchers said.
“The fossils from Jebel Irhoud display a modern-looking face and teeth, and a large but more archaic-looking braincase.”
Previously, the oldest securely dated Homo sapiens fossils were known from the site of Omo Kibish, in Ethiopia, dated to 195,000 years ago. At Herto, also in Ethiopia, Homo sapiens fossils are dated to 160,000 years ago.
Until now, most researchers believed that all humans living today descended from a population that lived in East Africa around 200,000 years ago.
“We used to think that there was a cradle of mankind 200,000 years ago in east Africa, but our new data reveal that Homo sapiens spread across the entire African continent around 300,000 years ago,” said lead author Professor Jean-Jacques Hublin, a paleoanthropologist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
“Long before the out-of-Africa dispersal of Homo sapiens, there was dispersal within Africa.”
“If we look at the history of human evolution, until the mid-1980s it was thought model humans evolved in Africa and shortly after migrated to Europe at around 40,000 years,” Prof. Grün added.
“In the 1980s there were the first results of anatomically modern humans in Israel at about 100,000 years.”
“In the 1990s there were a few sites found in Ethiopia dated to 200,000 years and now with these results the origins of modern humans are further pushed back to 300,000 years.”
A composite reconstruction of the earliest known Homo sapiens fossils from Jebel Irhoud, based on microcomputed tomographic scans of multiple original fossils. Dated to 315,000 years ago, these early Homo sapiens already have a modern-looking face that falls within the variation of humans living today. However, the archaic-looking virtual imprint of the braincase (blue) indicates that brain shape, and possibly brain function, evolved within the Homo sapiens lineage. Image credit: Philipp Gunz, MPI EVA Leipzig.
The new finds also reveal what was on the menu for our oldest-known Homo sapiens ancestors 300,000 years ago.
“Plenty of gazelle meat, with the occasional wildebeest, zebra and other game and perhaps the seasonal ostrich egg,” said Dr. Teresa Steele, a paleoanthropologist at the University of California, Davis.
The researchers sifted through hundreds of fossil bones and shells, identifying 472 of them to species as well as recording cut marks and breaks indicating which ones had been food for humans.
Most of the animal bones came from gazelles. Among the other remains, the team also identified hartebeests, wildebeests, zebras, buffalos, porcupines, hares, tortoises, freshwater mollusks, snakes and ostrich egg shells.
“Small game was a small percentage of the remains. It really seemed like people were fond of hunting,” Dr. Steele said.
“Cuts and breaks on long bones indicate that humans broke them open, likely to eat the marrow. Leopard, hyena and other predators’ fossils were among the finds, but we found little evidence that the non-human predators had gnawed on the gazelle and other prey.”
“The findings support the idea that Middle Stone Age began just over 300,000 years ago, and that important changes in modern human biology and behavior were taking place across most of Africa then,” she said.
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Jean-Jacques Hublin et al. 2017. New fossils from Jebel Irhoud, Morocco and the pan-African origin of Homo sapiens. Nature 546: 289-292; doi: 10.1038/nature22336
Daniel Richter et al. 2017. The age of the hominin fossils from Jebel Irhoud, Morocco, and the origins of the Middle Stone Age. Nature 546: 293-296; doi: 10.1038/nature22335
