The partial skeleton of a female Ardipithecus ramidus, nicknamed "Ardi", is estimated to be about 4.4 million years old.
This hominid seems to have been the ancestor to both humans and apes. However, evidence shows that she did not knuckle-walk but walked standing upright. This means that our ancestors walked straight over one million years ealier than previously thought.
This changes the theory that prevailed until now - i.e. humans must have been walking on all fours. Since apes also descend from Ardi but they knuckle-walk, this also means that knuckle-walking is an adaptation and that therefore apes evolved as much as humans did.
For more information read:
Discovery in Ethiopia casts light on human origins - Reuters .
Discovery of "Ardi" sheds light on human origins - The Vancouver Sun
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