Lucy

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…brain was not much bigger than a chimpanzee's . She was an ape with a human looking body but underdeveloped skull and brain. We obviously still had a long way to come in the 3.18 million years between then and now, but Lucy already showed clear differences from the normal apes. The shape of her hip bones and her upright posture means that Lucy is closer to us than the chimpanzee, the closest living relative of man.