Two fossil skeletons found in South Africa reveal a new species of hominid. They may provide an evolutionary link between the early hominid Australopithecus and our own Homo genus.
The two fossils were dubbed Australopithecus sediba. An adult female and adolescent male, the pair are thought to have fallen into a deep cave in Malapa, South Africa, around 1.9 million years ago, and remained there, more or less in place, until exposed to the modern elements.
The bones and teeth of the remains hint at an Austalopithecus which had many of the features of the later Homo genus. While they had the long arms and powerful hands of our earlier ancestors, the pelvis and legs strongly suggested the sedibas were capable of walking and running upright.
The pair were found by Prof. Lee Berger of the University of the Witwatersrand and his team, in an area near Johannesburg known as "the Cradle of Humankind". It's home to nearly a third of the sites associated with human origins. Berger used Google Earth to scout out new cave systems in the area. The caves where his team found the pair of hominids were filled with dead animals too, painting the picture of a death-trap, where creatures would fall to their doom - but their remains would be protected from roaming scavengers. Also preserved were bones of saber-toothed cats, antelopes, mice and rabbits
The researchers used uranium-lead radiometric dating on the fossils, and deduced that they're 1.78 to 1.95 million years old. This puts them at about a million years after so-called "missing link" Lucy — Austalopithecus afarensis. Current theories suggest that afarensis gave rise to africanus, and Berger posits that sediba would follow, an antecedent to our more immediate ancestors Homo habilis or even Homo erectus.
Two partial skeletons won't answer all our questions about our lineage, even if they are relatively complete given their age. But Australopithecus sediba is still an important piece in the puzzle of how humanity got to where it is now. This pair of hominids might be at the intermediate evolutionary stage between our more ape-like ancestors and our more recognizably human ones.
Image 1: The U.W. 88-50 (MH 1) cranium. The cranium forms part of the holotype skeleton of Australopithecus sediba from the Malapa site, South Africa. Photo by Brett Eloff courtesy of Lee Berger and the University of the Witwatersrand
Image 2: From Science, vol 328