Fine dining, if you’re Australopithecus bahrelghazali (Image: Don Emmert/AFP/Getty Images)

Our ancestors began eating grass half a million years earlier than thought, soon after they started leaving the trees. Early hominins, living 3 to 3.5 million years ago, got over half their nutrition from grasses, unlike their predecessors, who preferred fruit and insects.

This is the earliest evidence of eating savannah plants, says Julia Lee-Thorp at the University of Oxford. She found high levels of carbon-13 in the bones of Australopithecus bahrelghazali, which lived on savannahs near Lake Chad in Africa. This is typical of animals that eat a lot of grasses and sedges.

Previously, the oldest evidence of grass-eating was from 2.8 million years ago. The 4.4-million-year-old Ardipithecus ramidus, an early hominin, did not eat grass.


A. bahrelghazali may have eaten roots and tubers, rather than tough grass blades. Adding these to their diet may have helped them leave their ancestral home in east Africa for Lake Chad.

The question is whether hominins moved onto savannahs permanently, or went between woodland and savannah when it suited them, says Rick Potts at the Smithsonian National Museum of Natural History in Washington DC. “I would vote for the latter.”

Journal reference: PNAS, DOI: 10.1073/pnas.1204209109