Fossils of the earliest known hominins indicate that they walked upright on two legs but still spent a lot of time in trees. They don’t appear to have made stone tools and probably subsisted on a diet similar to that of chimpanzees and bonobos, our closest living relatives—which is to say mostly fruits, nuts, seeds, roots, flowers and leaves, along with insects and the occasional small mammal.

For the entire first half of our known history, hominins seem to have maintained this plant-based diet—they left no material trace of meat eating. It’s not until nearly three million years after our lineage got its start that there’s any evidence that they exploited large animals for food.

The oldest possible evidence of meat eating by hominins comes from Dikika, Ethiopia. There researchers found fragments of bone from goat- and cow-size mammals bearing marks suggestive of butchery that occurred at least 3.39 million years ago.

The butcher, in this case, was probably Australopithecus afarensis, the small-brained, small-bodied hominin species to which the famous Lucy fossil belongs—the only hominin species known from this time and place. Although no tools were discovered, based on the pattern of damage to the bones, the researchers concluded that A. afarensis used sharp-edged stones to strip flesh from the bones and struck the bones with blunt stones to access the marrow inside.