"Gorilla molars are relatively high crowned and have shearing crests, which are advantageous for the breakdown of leaves," Macho said.
In contrast, the shape of the hominid teeth and their internal enamel structure, suggests the early humans combined shearing with lateral lower jaw movement.
"Chew a toffee and feel the difference," Macho said, comparing this type of chewing with eating a brittle food, like a roasted peanut, which involves more up and down motion. Although he thinks the ancient humans ate certain nuts, including the peanut-like groundnut, their teeth suggest brittle edibles were mostly absent from their diet.
University of California at Berkeley paleontologist Tim White co-directed the recent project that brought to light the "Ardi" skeleton and Ardipithecus ramidus, which lived 4.4 million years ago.
White agrees that Australopithecus molars had thick enamel "more durable to heavy chewing of hard and tough foods with adhering grit," he told Discovery News. Ardi likely consumed a similar diet and "was probably omnivorous," according to White and his team, who add that mushrooms were also probably on the prehistoric menu.