A long time ago, by the shores of a lake in East Africa, a group of hungry foragers tucked into a primeval steak dinner. They carved the meat of cow- and goat-sized animals with sharp stone tools and smashed the bones to get at the rich marrow inside. The scene is remarkable mainly because it happened 3.4 million years ago, pushing back by 800,000 years the earliest known example of hominids using stone tools and eating meat.

The foragers in question were likely members of the primitive genus Australopithecus, specifically A. afarensis, the species to which the celebrated Lucy fossil belongs. Scientists had long believed that the australopithecines, whose teeth and jaws were adapted for eating fruit, seeds and other plant foods, were primarily vegetarian. But the new finds—cut-marked animal bones recovered from a site called Dikika, just a few kilometers from the Lucy site in Ethiopia’s Afar region—suggest that “we could now be looking at an extended period of time when [hominids] were including meat in their diet and experimenting with the use of stone tools,” observes lead study author Shannon P. Mc­Pher­ron of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. A report describing the bones appeared in the August 12 issue of Nature.

What prompted this dietary switch? Some archaeologists believe ecological shifts may have led the species to seek new sources of sustenance. “It may be that behavioral adaptations allowed A. afarensis to adapt to these environmental perturbations with­out anatomical changes,” surmises archaeologist David R. Braun of the University of Cape Town in South Africa.

Critics have questioned whether the marks really did come from stone tools, partly because none were found at the site. Future discoveries are likely to resolve that question. “I think we will start seeing many more people searching more intently ... for this type of evidence,” Braun predicts.