It's all in the wrist: Humans lack a knuckle-walking ancestor (EARTH Magazine)

October 1, 2009
Zahra Hirji


Though counterintuitive, scientists have turned their attention away from the feet and to the wrist and forearm to better understand how humans evolved upright walking, or bipedalism. African apes are humans’ closest living relatives, and because these apes knuckle-walk, some paleoanthropologists have suggested that African apes and humans share a knuckle-walking ancestor. A new study, however, reveals that lumping the locomotion of all African apes together is a mistake: Knuckle-walking may have evolved more than once in the ape lineage. Therefore, the researchers say, humans probably did not evolve from a knuckle-walker but instead from a more general tree-dweller.

All African apes — gorillas, chimpanzees and bonobos — knuckle-walk. The scientists who think that humans have a knuckle-walking heritage bolster the claim by pointing to the fact that modern and ancient humans, or hominins, such as Lucy (Australopithecus afarensis), retain several wrist and forearm features that are supposedly knuckle-walking adaptations, says Tracy Kivell, a paleoanthropologist at Duke University in Durham, N.C., and co-author of the study published in Proceedings of the National Academy of Sciences.

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