You wait ages for a new human species, and then two come along at once. Hard on the heels of the discovery of a new type of hominin in Siberia, an international team says it's found the closest yet type of australopithecine to modern humans.
The two partial skeletons, dating from between 1.78 and 1.95 million years ago, were discovered in South Africa, just nine miles from the Sterkfontein World Heritage Site, known as the Cradle of Humankind.
Dubbed Australopithecus sediba, the new species differs from other australopiths and shares significant features with modern humans, such as increased buttressing of the ilium, expansion of the posterior ilium, and a decrease in the distance between the hip joints and sacroiliac.
It also differs from the earlier australopiths in having reduced cranial muscle markings, more delicate facial morphology and smaller teeth. But it shares with them a small body size and longer upper limbs with large joint surfaces.
The discovery suggests that the transition between the small-bodied Australopithecus africanus and the bipedal Homo erectus occurred not only in East Africa, but across the whole of African, including South Africa.
"The discovery is an amazing one. It's late enough that it is contemporaneous with our ancestors that were, at the time, evolving into Homo erectus. The fossils in South Africa tend to be very rugged, with heavy faces and huge molars. These aren't like that, and suggest that they're related to East African fossils that many have put in the taxon Homo habilis," said Indiana University anthropology professor Kevin Hunt.
"The intriguing thing is that they still have traits found in the more rugged species, Australopithecus africanus, that is found half a million to a million (or more) years earlier. This suggests that just like humans all over the world have evolved but retained their regional characteristics, we had regional characteristics of Homo habilis at two million years ago."
The research appears in Science.