The origins of the species remain surprisingly obscure. But the two skeletons, unusually, suggest our ancestor may have climbed back up into the trees – after having evolved to walk on the ground.
It was around 2 million years ago that the first humans evolved from smaller-brained australopiths. The precise species that gave rise to humanity has never been found, but it seems that Australopithecus sediba, discovered in 2008, was very closely related to it.
A new set of studies, published in Science, confirm that A. sediba carried a bizarre mosaic of ancient australopith and modern Homo features – making it possible that the fossils are an "ideal ancestral form of the genus Homo", says Peter Schmid at the University of Zurich, Switzerland.