Grass-eating hominid was the primate equivalent of a cow

Although the ancient hominid Paranthropus boisei has earned the nickname "Nutcracker Man", his actual diet was quite a bit softer. Unlike any other known human ancestor, this ancient hominid's powerful jaw and huge molars were actually used to eat grass.

Researchers had long known that Paranthropus boisei used his huge mouth to crush nuts, seeds, and hard fruits. Its anatomy included extremely powerful jaw muscles and the largest, flattest molars of any known hominid. But careful analysis on the wear marks of its teeth tell a different story, revealing that he was actually eating soft fruits or grass. In this new scenario, his powerful mouth was used not to crush hard foods but to take in as much grass as possible in a single sitting.

University of Colorado anthropologist Matt Sponheimer explains:

"Frankly, we didn't expect to find the primate equivalent of a cow dangling from a remote twig of our family tree. Fortunately for us, the work of several research groups over the last several years has begun to soften prevailing notions of early hominid diets. If we had presented our new results at a scientific meeting 20 years ago, we would have been laughed out of the room."

Paranthropus boisei is, in evolutionary terms, sort of a great-uncle of modern humans. Around 2.5 million years ago, our common ancestors the Australopithecines split into two new genuses, Homo and Paranthropus. While the new Homo genus ultimately led to our development, Paranthropus represented a dead end, with all members of the genus eventually going extinct.

Anthropologists had assumed that one major reason the genus died out was picky eating habits. But the old picture of Paranthropus only eating nuts and seeds has slowly fallen away, and this new evidence of boisei's grass diet suggests the genus was willing to eat anything. That means it's more likely that Homo simply out-competed Paranthropus, with our genus using newfound technology to outlast boisei and his sibling species.

Via PNAS