Humans emerged on one very young twig on the vertebrate branch. Humans and chimps diverged from a common ancestor 5- 7 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.

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. Examine the above timeline of human evolution.

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 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..