Two remarkably complete skeletons of Australopithecus sediba, found in 2010, are leading scientists to rethink when and how the genus, Homo, evolved. New findings about this 2-million-year-old species revise our picture of the origin of the human lineage.
Previously, brain enlargement and the birth of larger-brained babies were considered critical factors in the origin of Homo. New research on the fossil skeletons of Au. sediba show, however, that important changes in the pelvis and outer surface of the brain occurred prior to brain expansion.
Traits typically found in either Australopithecus or Homo are combined in the hand and foot fossils of Au. sediba. The powerful thumb suggests that Au. sediba made stone tools, yet other parts of the hand and foot indicate that it regularly climbed trees.
Australopithecus sediba offers a snapshot of evolution between 2.0 and 2.4 million years ago, when several important hallmarks of the human lineage arose.
The new findings were announced September 8, 2011, in the journal Science.
Photograph of Australopithecus sediba skeleton; image credit Smithsonian's Human Origins Program.