Almost two million years after their last meals, two members of a prehuman species in southern Africa left traces in their teeth of what they had eaten then, as well as over a lifetime of foraging. Scientists were surprised to find that these hominins apparently lived almost exclusively on a diet of leaves, fruits, wood and bark.

If you are what you eat, the new research and other recent studies suggest there was more diversity in the diets of early prehumans, both within and between species, than previously understood. And this could in part account for the recently recognized physical diversity among the long intermediate line of hominins belonging to the genus Australopithecus.

The dietary pattern of the enigmatic species, Australopithecus sediba, discovered four years ago in the Malapa caves northwest of Johannesburg, was unexpected for several reasons. It contrasted sharply with available data for other hominins in the region and elsewhere in Africa; they mainly consumed grasses and sedges from the savanna....