The story of humans, once again, has been rewritten.
Researchers have recently dated the "Broken Hill skull", an important extinct hominid skull discovered in the 1920s, and found it’s some 200,000 years older than previously thought. This means the time of hominin ancestry needs a fairly major rethink. The revised dating suggests this extinct species might have shared the African continent with other hominins, including none other than Homo sapiens (that’s us).
The Broken Hill cranium was recovered during metal ore mining in 1921 in present-day Zambia. It was originally designated as a new species, Homo rhodesiensis, although most contemporary scientists argue it belonged to the species Homo heidelbergensis, a Middle Pleistocene species from Europe and Africa.
This wasn’t the only controversy that arose from the skull. Most of the site was disrupted by quarrying, destroying much of the evidence that could help researchers date the specimen. Initial estimates dated the skull to around 500,000 years ago. However, the new research published in the journal Nature concluded that the skull is about 299,000 years old.
The skull, one of the best-preserved fossils of H. heidelbergensis ever discovered, can currently be found in the Natural History Museum in London. The team reassessed its age using radiometric dating methods on the skull and the dusty sediment recovered from the excavation site, estimating it is between 274,000 and 324,000 years old.
This has several big implications, not least because H. heidelbergensis is thought to be have been a key character in the story of human evolution. The ancestral connection between H. heidelbergensis to modern humans is uncertain, and this new dating makes things even more complex as it suggests that Africa was home to co-existing diverse human lineages some 300,000 years ago.
“This [skull] is surprisingly young, as a fossil at about 300,000 years would be expected to show intermediate features between H. heidelbergensis and H. sapiens, but Broken Hill shows no significant features of our species," Professor Chris Stringer, research leader in Human Origins from the Natural History Museum, explained in a statement.
“Previously, the Broken Hill skull was viewed as part of a gradual and widespread evolutionary sequence in Africa from archaic humans to modern humans. But now it looks as if the primitive species Homo naledi survived in southern Africa, H. heidelbergensis was in south-central Africa, and early forms of our species existed in regions like Morocco and Ethiopia,” added Stringer.