Oldest Known Human Fossils May Push Back Homo sapiens Evolution 100,000 Years

Recently discovered human fossils may changed our understanding of prehistory.

The fossils are estimated to be about 300,000 years old, a full 100,000 years older than the previous oldest fossils, scientists reported Wednesday. Plus, they were found at a site in Morocco, supporting the theory that Homo sapiens evolved across Africa rather than in East Africa alone.

A reconstruction of a mandible of the earliest known human fossils from Jebel Irhoud, Morocco.

The story of their discovery starts back in 1961, when mining operations at a Moroccan site called Jebel Irhoud unearthed a skull. That led to further excavations. The fossils unearthed at the time there were incorrectly determined to be 40,000-year-old Neanderthal remains. They were later re-dated at 160,000 years old, but there was lingering uncertainty about their geologic age as their exact location was not recorded.

Archaeologists returned to the site in 2004 and have since uncovered the remains of at least five individuals. But they didn’t just find people—there were tools and animal remains as well, a startlingly rich cache of fossils and artifacts.

Among the artifacts were fire-singed stone tools found in the same layer as the hominid remains, a lucky discovery that enabled the team  to determine the age of the tools using thermoluminescence dating, a technique that requires the object to have been heated at the time to nearly 1,000˚ F or more. Together with analysis of one of the human teeth found during the 1960s excavations along with other materials in the layer, they re-dated the site to about 300,000 years old.

The excavation site at Jebel Irhoud, Morocco.

Here’s Ed Yong, reporting for The Atlantic:

It’s not just when these people died that matters, but where. Their presence in north Africa complicates what was once a tidy picture of humanity arising in the east of the continent. “What people, including myself, used to think was that there was a cradle of humankind in East Africa about 200,000 years ago, and all modern humans descend from that population,” says Philipp Gunz from the Max Planck Institute for Evolutionary Anthropology, who was involved in the new excavation. “The new finds indicate that Homo sapiens is much older and had already spread across all of Africa by 300,000 years ago. They really show that the African story of our species was more complex than what we used to think.”

Using tomographic scans similar to X-rays and 3D statistical shape analysis, the scientists determined that the individuals at Jebel Irhoud probably would have had faces just like modern humans. There was one key difference, though—the braincase indicate that “brain shape, and possibly brain function, evolved within the Homo sapiens lineage,” Gunz said in a statement.

Follow our ancient ancestors’' footsteps out of Africa and into every corner of our planet.