Twenty years ago, scientists discovered a 7-million-year-old skull that they concluded belonged to a creature who walked upright and was our earliest known ancestor. Not everyone was convinced. Now, the researchers are back with more evidence 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 instead of on all fours. When early humans started walking upright, it marked a key moment in our split away from apes
