A team from the University of the Witwatersrand in Johannesburg, South Africa, has revealed two remarkably well preserved hominin fossils aged just under two million years old. The fossils were discovered at Malapa cave, part of a site known as the Cradle of Humankind, some 40 kilometres west of Johannesburg. But the researchers' suggestion that the fossils represent a transitional species in human evolution, sitting between Australopithecus and Homo species, has been criticized by other researchers as overstated. The fossils, a juvenile male and an adult female, were found together in the Malapa cave, part of an eroded cave system, leading to speculation that the two fell to their deaths while searching for water. The fragile parts of the skeleton that are often missing from fossils this old, such as the hands and feet, have been preserved (see videos showing fossilized cranium here and here). The collar bone of the first specimen was discovered by team leader Lee Berger's nine-year-old son during a visit to the site in 2008.
Controversially, the researchers have named the fossils as a new species, Australopithecus sediba. 'Sediba' means fountain or wellspring in Sotho, which is one of the 11 official languages of South Africa. Berger deems this an appropriate name, as he says that A. sediba is a good candidate for being the transitional species between the southern African hominin, Australopithecus africanus, and early Homo species — either the earlier Homo habilis or even a direct ancestor of the more recent Homo erectus. The research is published in Science. But palaeoanthropologist Tim White of the University of California, Berkeley, says that A. sediba and A. africanus are merely chronospecies: names given to describe slightly different anatomy in fossils from a single evolving species. White says that the suggestion by Berger and his team that this lineage split before the emergence of Homo is “fossil-free speculation”, adding that “the obsession with Homo in their title and text is difficult to understand outside of a media context”.