Homo Erectus in Eurasia
They found stone artefacts — mostly flakes that were dropped as hominins knapped rocks to create tools for butchering animals — lying in sediments almost 1.85 million years old. Until now, anthropologists have thought that H. erectus evolved between 1.78 million and 1.65 million years ago — after the Dmanisi tools would have been made.
Furthermore, the distribution of the 122 artefacts paints a picture of long-term occupation of the area. Instead of all the finds being concentrated in one layer of sediment, which would indicate that hominins visited the site briefly on one occasion, the artefacts are spread through several layers of sediment that span the period between 1.85 million and 1.77 million years ago. The findings are published today in the Proceedings of the National Academy of Sciences1.
“This is indeed suggestive of a sustained regional population which had successfully adapted to the temperate environments of the southern Caucasus,” explains Wil Roebroeks, an archaeologist at Leiden University in the Netherlands.
The presence of a tool-using population on the edge of Europe so early hints that the northern continent, rather than Africa, may have been the evolutionary birthplace of H. erectus. Unfortunately, the fossils of the hominins responsible for making the tools are not proving very helpful to the debate.
Fossilized bone fragments found in the same sedimentary layers as the Dmanisi artefacts are too weathered to be identified as belonging to any one species, so it is impossible to say for sure whether the tools were made by H. erectus.
Neither do fossil skulls previously retrieved from later sediments at the site help to resolve the controversy. These fossils, dating from 1.77 million years ago, had brains between 600 and 775 cubic centimetres in volume, whereas H. erectus is generally thought to have had an average brain size of around 900 cubic centimetres. For comparison, modern humans have a brain capacity of around 1,350 cubic centimetres. “Many people call those Dmanisi fossils the earliest H. erectus, but there is still frequent debate about this,” explains Ferring.