13:46 12 August 2012
Fossils uncovered in northern Kenya have revealed a major breakthrough in human development; they have been used to identify new species.
The discoveries, which were backed with research published in the journal Nature, suggests that at least three distinct species of humans previously co-existed in Africa.
Finds like this are establishing a case to disprove the popular theory that there was a linear evolution from early primates into modern humans.
Three human fossils were dug up - one face and two jawbones complete with teeth - which are between 1.78 and 1.95 million years old.
These help to assert the importance of a find back in 1972 that saw a skull uncovered that was very different from many others thanks to its larger brain and longer, flater face. However, because there was only one example discovered, it was impossible to establish if that skull (known as Homo rudolfensis) was an individual one-off or a member of a new species. These new finds point to the latter.
The oldest known ancestor of the human race dated back to 1.8 million years ago and was known as Homo erectus - they had smaller heads, larger brows and stood upright.
But 50 years ago, researchers discovered an even more primitive species which they named Homo habilis which possibly co-existed with that. And now that it's thought that Homo rudolfensis was around too, it suggests that many species of human were co-existing in the same period.
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