Diet has long been hypothesized as a driver of change among hominins, especially with regard to the increase in brain size. Dietary niches reconstructed based on these fossils showed that the Australopithecus individuals had diets very similar to both contemporaneous and modern herbivores but different from carnivores.
ha, yeah, I noticed that too, but its a graph of brain size over millions of years, so its close enough to illustrate the point that something big happened 2-3 million years ago.