Posted on June 24, 2011

Human Ancestors in Eurasia Earlier Than Thought

Matt Kaplan, Nature News, June 6, 2011

Archaeologists have long thought that Homo erectus, humanity’s first ancestor to spread around the world, evolved in Africa before dispersing throughout Europe and Asia. But evidence of tool-making at the border of Europe and Asia is challenging that assumption.

Reid Ferring, an anthropologist at the University of North Texas in Denton, and his colleagues excavated the Dmanisi site in the Caucasus Mountains of Georgia. They found stone artifacts–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 artifacts 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 artifacts 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 Sciences.


Eurasian ancestry?

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.


There and back again

Even if the ancient inhabitants of the Dmanisi site were not early members of H. erectus, there is still a problem: anthropologists have previously thought that no hominins existed outside of Africa as early as 1.85 million years ago.

“Anthropology textbooks of the 1990s often showed maps with large arrows indicating migration of early H. erectus from its inferred core area of eastern Africa to other parts of the Old World,” explains Roebroeks. The findings in Dmanisi make such an explanation look faulty.