NEW YORK (AP) — Twenty years ago, scientists discovered a 7-million-year-old skull they concluded belonged to an upright-walking creature that was our oldest known ancestor. Not everyone was convinced. Now, investigators are back with more evidence that they say strengthens their case.
Their new study published Wednesday analyzed arm and leg fossils found near the skull in Africa, looking for signs of walking on two feet rather than four legs. When the first humans began to walk upright, it marked a key moment in our separation from the apes.