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Excavations at an archaeological site in Morocco have identified the earliest known fossils of our species, Homo sapiens.
The human remains and stone tools found at the site are between 350,000 and 280,000 years old. This new fossil evidence pushes back the earliest examples we have of the Homo sapiens lineage by more than 100,000 years.
The discoveries, found in Jebel Irhoud in Morocco, help fill in the patchy fossil record for our species and could lead scientists to revise their ideas about human evolution in Africa.
Museum human origins expert Prof Chris Stringer comments: 'These finds currently represent the oldest association of probable early members of the Homo sapiens lineage and Middle Stone Age tools. They shift Morocco from a supposed backwater in the evolution of our species to a prominent position.'
Fossils were first found in Jebel Irhoud in the 1960s, but were originally estimated to be about 40,000 years ago. At the time, these fossils didn’t fit with any working theories of human origins, so they were considered a curiosity.
Later work in the 1990s dated the bones to between 200,000 and 100,000 years old. However, new work using improved dating methods, led by researchers from the Max Planck Institute for Evolutionary Anthropology in Germany, revealed that these fossils are even older.
The scientists later excavated more human fossils from the site, including a partial skull and a lower jaw, as well as stone tools found alongside the bones. A technique called thermoluminescence dating aged the tools at around 350,000-280,000 years old.
Meanwhile, fresh examination of a previously discovered fossil tooth shifted its estimated age from around 160,000 to around 318,000-254,000 years old, putting it in the same timeframe as the tools.
The researchers compared the shape of the Irhoud fossil skull faces with a range of early and recent human relatives, such as Neanderthals. Their study showed that facially, the Irhoud specimens were most similar to modern Homo sapiens.
Being early examples of the Homo sapiens lineage, the skulls show a mixture of modern and archaic human features. Prof Stringer explains:
'The Irhoud fossils display some primitive features such as a longer, lower braincase, strong browridges, and a large face and teeth, as one might expect at around 300,000 years old. Yet the delicate cheekbones and retracted face look more modern, as do details of the skulls and teeth, and the shape of the jawbones.'
No-one knows exactly when Homo sapiens evolved in Africa from ancestral humans within the genus Homo. However, current evidence from both fossils and DNA, says Prof Stringer, suggests that modern human and Neanderthal lineages separated at least 500,000 years ago. We should therefore be able to discover early examples of both lineages.
Indeed, early Neanderthal fossils have been found at the Sima de los Huesos (Pit of the Bones) site in Spain, dating to around 430,000 years ago. But the earliest fossils so far discovered that look anatomically similar to modern humans are from Omo Kibish in Ethiopia and date to around 200,000 years ago.
There is therefore a large gap in the story of how the Homo sapiens lineage developed, which the Irhoud research helps to fill.
Prof Stringer thinks that other fossil discoveries may also need to be looked at again. He says, 'It is possible that earlier and neglected fossils from sites such as the Salé and Thomas Quarries in Morocco, and Ndutu in Tanzania, could be even more ancient members of our species, Homo sapiens.'
Prof Stringer agrees with the researchers that, as more examples of the early Homo sapiens lineage are discovered, the gap between anatomically archaic and modern is likely to disappear.
How the Irhoud material fits into the bigger picture of Homo sapiens development in Africa is not yet clear, he says, but it adds to the complex picture of different human forms and lineages co-existing on the continent.
Prof Stringer adds, 'It is likely that different early Homo sapiens populations already existed in different parts of Africa about 300,000 years ago, as well as surviving examples of the more ancient lineages of Homo heidelbergensis (also classified by some as Homo rhodesiensis) in Central Africa and Homo naledi in the South.