After analyzing a 1.8 million-year-old skull, researchers suggested different "species" of hominids such as Homo habilis, and Homo erectus were actually of the same kind and just looked different.
The remains in question were uncovered in Dmanisi, Georgia. The skull, dubbed Skull 5, was unusual because it had a small brain casing and long teeth, which is not generally seen in Homo fossils, an American Association for the Advancement of Science news release reported.
Skull 5 was discovered among the remains of four other hominids from the same time period, as well as animal fossils and ancient stone tools. There may be even more wonders on the site, which has not yet been entirely excavated.
David Lordkipanidze, from the Georgian National Museum, said the difference between these early Homo species were no more pronounced than the difference between five modern humans.
"Had the braincase and the face of Skull 5 been found as separate fossils at different sites in Africa, they might have been attributed to different species," study co-author Christoph Zollikofer of the Anthropological Institute and Museum, said.
"[The Dmanisi finds] look quite different from one another, so it's tempting to publish them as different species. 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," he said.
The Dmanisi fossils walked the Earth during the early Pleistocene epoch, which was not long after "Homo diverged from Australopithecus and dispersed from Africa," the news release reported.
The Skull 5 jawbone was found five years before the rest of the skull, but when the pieces were all put together the skull was found to be the most massive ever discovered on the site. It measures at about 546 cubic centimeters, suggesting the skull contained a small brain in comparison to its human-like body.
"Thanks to the relatively large Dmanisi sample, we see a lot of variation," Zollikofer said. "But the amount of variation does not exceed that found in modern populations of our own species, nor in chimps and bonobos."
"Furthermore, 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," he said. "And since the Dmanisi hominids are so similar to the African ones, we further assume that they both represent the same species."
These findings indicate Homo fossils may be all of the same species, rather than several "ecologically specialized" species.
