Ancient Skull Suggests New Story of Human Evolution

A recent discovery of a 1.8 million-year-old skull suggests that all the earliest members of the Homo genus belonged to the same species.

Unearthed in Georgia, the fossil, called Skull 5, combines a small braincase with a long face and large teeth. In fact, had the two features been found at different sites, "they might have been attributed to different species," argues co-author Christoph Zollikofer from the Anthropological Institute and Museum in Zurich, Switzerland.

The fact that the remains of four other early human ancestors were discovered beside it has allowed researchers the first chance to compare physical traits of individuals that apparently lived during the same period and in the same place, suggesting they all represent the same species. Under any other circumstance, however, they would have likely been classified differently, the researchers say.

"[The Dmanisi finds] look quite different from one another, so it's tempting to publish them as different species," Zollikofer explained. "Yet we know that these individuals came from the same location and the same geological time, so they could, in principle, represent a single population of a single species."

The fossils date back to the early Pleistocene epoch, a time shortly after the great migration out of Africa. It took five years to discover all the pieces of Skull 5 and put it together. Once researchers did this, however, they realized they had unearthed the site's largest skull.

"Thanks to the relatively large Dmanisi sample, we see a lot of variation," Zollikofer explained. "But the amount of variation does not exceed that found in modern populations of our own species, nor in chimps and bonobos.

"Furthermore," he continued, "since we see a similar pattern and range of variation in the African fossil record...it is sensible to assume that there was a single Homo species at that time in Africa. And since the Dmanisi hominids are so similar to the African ones, we further assume that they both represent the same species."