Orrorin walks
Thigh bones from Kenya, six million years old, carry the internal structure of a habitual biped.
- When
- —
- Duration
- 400 thousand years
- Known to
- ± 200 thousand years
- Era
- Miocene, Cenozoic
Orrorin tugenensis is known from teeth and postcranial fragments from the Tugen Hills, of which the femora are the most informative: the neck is long and the cortical bone is distributed asymmetrically in the pattern produced by the loading of upright walking. Its arm and finger bones also indicate it still climbed. Together with Sahelanthropus and Ardipithecus, it makes bipedalism the earliest identifiable hominin trait — walking upright comes long before brain expansion, tools, or anything else.