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• Humans emerged on one very young twig on the vertebrate branch. • Humans and chimps diverged from a common ancestor 57 million years ago. • Q: Are our ancestors chimps or modern apes? • A: No. We represent 2 divergent branches of the anthropoid tree that evolved from a common ancestor. • Chimps are more like our cousins or siblings, but not our parent species. •Examine the above timeline of human evolution. • Q: Is human evolution a ladder with a series of steps leading directly from an anthropoid ancestor to Homo sapiens? • A: No. It is like a multibranched bush; many splinter groups have traveled down dead ends. Several different human species coexisted. Our species is the tip of the only twig that still lives. • Q: Did human characteristics, such as upright posture and enlarged brain, evolve in unison? • A: No. Different human features evolved at different rates, with erect posture, or bipedalism, leading the way. Ex: We had ancestors who walked upright, but still had ape-sized brains. • KINDS OF HOMINIDS: • I. Australopithecus (came before Homo genus) walked African savanna. • A. afarensis = early species, was bipedal • One of most complete fossil skeletons of A. afarensis was found (see left); was nicknamed “Lucy” by her discovers. • (“Lucy in the Sky with Diamonds” song was playing on radio when she was discovered.) • Was female, 3’ tall, softball size head, 3.2 million years old in East Africa. • Australopithecus species extinct by 1.4 million years ago. Lucy • Hominid bipedal footprints discovered in Tanzania, East Africa in 1978. • Are 3.7 million years old. Evidence that bipedalism is a very old human trait. • A. afarensis skull, 3.9 million years old, with a vertical backbone. • Evidence that upright posture is at least that old..