Australopithecus sediba

In August 2008, nine-year-old Matthew Berger, chasing his dog at the Malapa site in South Africa's Cradle of Humankind, spotted a fossil collarbone sticking out of a rock. His father, the paleoanthropologist Lee Berger, led the excavation that followed. It yielded the partial skeletons of a young male and an adult female, dated in 2011 to about 1.98 million years ago, and in 2010 the team named them Australopithecus sediba. 'Sediba' means 'wellspring' in the Sotho language. The brain was small, about 420 cubic centimetres, and the arms were long and apelike.

What made the find startling was the mix of traits. The pelvis, the hands with a relatively long thumb and short fingers, and the teeth look more like early Homo, while the shoulders and ankles look more like those of earlier australopithecines. Berger and colleagues proposed that sediba might be a direct ancestor of Homo. Many other researchers disagree, pointing out that fossils assigned to Homo are already older than sediba, so it more likely belongs to a surviving australopith lineage that evolved some Homo-like features by itself. Either way, the fossils show how varied our relatives were two million years ago, and how a single skeleton can overturn tidy family trees.