And with that conclusion about an old foot, they really stepped in it. Their claim has inflamed one of the hottest debates on human origins: when did our ancestors leave the trees? A faction led by Owen Lovejoy of Kent State University argues that the legs, hips and spines of australopithecines like the famous Lucy were adapted for walking upright. an all-or-nothing advance. To conclude. based on a toe. that Lucy also swung through trees is “patently absurd,” he told Science. Randall Susman of the State University of New York disagrees. If our ancestors had toes adapted for grasping branches, he says, they used them for grasping branches.
If this sounds like the feud of academics with too much free time, in fact it hides a key debate in evolutionary theory. Scientists like Susman believe that if a creature has some trait-like a grasping big toe-that trait exists because it is useful for survival. Others argue that a trait might exist just by happenstance, or as a vestige. Now. forget “big toes” and substitute behaviors such as male promiscuity and female nurturing. One camp says that all traits are the products of natural selection, and hence say something profound about human nature. The other argues that some are artifacts, shedding little light on the human condition. It’s not just about toes.
