The most comprehensive dataset ever assembled on our early human ancestors provides evidence that the first humans emerged in South Africa, and that the first humans to migrate out of Africa came from a small-bodied species such as Homo habilis, aka "Handy Man."
The theory is a complete shake-up of the human family tree, since it has long been theorized that a relatively tall, muscular human, Homo erectus (Upright Man), was the first to leave Africa for Asia and Europe.
Traditionally, Handy Man "was viewed as a little human, with a relatively big brain, bipedalism, and tool-making forming part of the picture," said Mark Collard, a professor at Simon Fraser University's Human Evolutionary Studies Program and Department of Archaeology, and senior author of the study in Proceedings of the Royal Society B.
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Collard, however, added that a revised view of Handy Man is that this human was much more ape-like than us, combining walking on two legs with frequent climbing.
Since the scrappy individuals were thought to have been a favorite snack of non-human predators at the time, one can imagine that Handy Man had to be handy with his feet as well when he was threatened.
For the study, Collard and his team compared alternative human evolutionary trees, seeing how well they fit the newly constructed dataset. The output from each, he explained, was a statistic representing one of the following: it was consistent with the dataset, it was not consistent and therefore could be rejected, or it fell somewhere in the middle.
The study rejected the theory that Homo floresiensis individuals, "Hobbit Humans," were simply deformed members of our own species. The data instead shows that these tiny residents of the Island of Flores, Indonesia, did indeed belong to a unique species. Collard and his team suspect that the hobbits descended from a small-bodied early Homo species, such as Handy Man.
Following this theory, Handy Man gave rise to Upright Man in Asia.
"Homo erectus would then have spread from Asia into Africa, rather than the reverse, which is what the current consensus contends," Collard said.
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As for Neanderthals, "We're pretty sure that Neanderthals are an exclusively Eurasian species; there is no evidence for them in Africa," he shared.
The species that gave rise to Neanderthals remains a mystery for now. This puzzlement about them, and other Middle Pleistocene humans, is referred to as "the muddle in the middle," Collard said.
Somewhat less confusing is the evidence on where the first humans likely emerged. The researchers plugged in information concerning the two-million-year-old human ancestor Australopithecus sediba, to help make that determination.
"The fact that Australopithecus sediba groups with Homo is consistent with the idea that the earliest known representative of the genus Homo originated in South Africa," Collard said.
Terry Harrison, director of the Center for the Study of Human Origins and New York University, where Harrison is also a professor, told Discovery News that the new study "will surely spark passionate debate on all sides of the paleoanthropological community."
Bernard Wood, a professor of human origins at George Washington University, calls the new study "a landmark publication." He explained that the researchers have "begun the process of deepening our present very superficial understanding of human evolutionary history."
Collard hopes that his team's results will encourage other scientists to pursue research in South Asia, Southeast Asia and China, where the remains of some of the earliest humans outside of Africa could be found.