One tiny bone ignites evolutionary fervour

by Carl Wieland

Perhaps not since the fabled “Nebraska Man” (and his family) were touted as human ancestors, based on a tooth later found to be from a pig, has there been this much fuss about a single bone.1

The bone in question is a fourth metatarsal (shown in a human foot in the X-ray here). It was allegedly found along with some other remains of Australopithecus afarensis, the same type of creature as the famous fossil ‘Lucy’.

Found by Donald Johanson in 1974, Lucy had no foot bones or skull, but most of the rest of her skeleton was substantially present. She became a ‘poster child’ for human evolution, and was regarded as our definite ancestor.

Johanson himself (who may not be the most disinterested of parties in all this) is in fact one of the co-authors of the Science paper causing all the excitement.2 This diminutive bone and its slight curvature is said to be enough to show that the feet of Lucy’s kind had medial arches, like humans do. These stiffen the feet, and are associated with habitual upright walking. The feet of creatures that spend a lot of time in trees, like apes, are not stiffened like that at all, but are able to curve and flex to grasp to an extent.

Richard Potts, from the Smithsonian Museum’s human origins program, said that the report was “an impressive paper for just one bone.” He was not being sarcastic; he said the bone was a “game-changer” for him.3….

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