Many scientists have argued that several different species of human ancestors spread from Africa—but a 1.8 million-year-old skull and the fossilized remains of four other creatures seem to tell a different story. The scientists who found the bones at Dmanisi, in the country of Georgia, in 2005 say they show that a single species fanned out from the continent, the Wall Street Journal reports. "There are these jaw-dropping moments in the life of a scientist," says a neurobiologist who examined "Skull #5," as it's called. "Preconceived ideas ... start falling to pieces." The crux of the finding:
- Scientists have for years debated whether humans evolved from only one or two species (think tree branches out from a trunk) or many off-shoots that dead-ended (think a bush). This find bolsters the tree theory. The bones found in Georgia show a great deal of variation, but the pre-humans are believed to have died in the same place, within a few centuries of each other. So the researchers believe they are members of the same species, and reason that it's likely the various skulls found in different places and times in Africa may not be different species, but variations of one species.
Even aside from the tale it tells, the skull is a pretty impressive discovery. "It's got to be one of the most complete skulls ever discovered in the fossil record of human evolution," an anatomy professor tells NPR. And as the oldest batch of pre-human fossils found outside Africa, the bones set the date of departure from Africa "much earlier" than previously believed, David Lordkipanidze, the lead author of the study published in Science, tells the AP. (Previously, that movement was thought to have happened 1 million years ago.) With the Dmanisi finds, "For the first time, we can see a population. We only had individuals before," says another researcher. (Read more skull stories.)