An early human ancestor likely did not eat hard foods as previously suggested because it did not have the jaw necessary for such foods.

Published in the journal Nature Communications, the new study contradicts research from 2012 that found Australopithecus sediba to have included hard foods like nuts in its diet. The new study indicates the Australopithecus did not have a jaw that could break up hard foods.

"Most australopiths had amazing adaptations in their jaws, teeth and faces that allowed them to process foods that were difficult to chew or crack open. Among other things, they were able to efficiently bite down on foods with very high forces," Dr. David Strait, a professor of anthropology in Arts and Sciences at Washington University in St. Louis who lead the research team, said in a press release.

The researchers used computer modeling to simulate tests on a fossilized Australopithecus skull unearthed in 2008. They used biomechanical tests engineers have used to test the impact endurance of various machines.

"Australopithecus sediba is thought by some researchers to lie near the ancestry of Homo, the group to which our species belongs," Dr. Justin Ledogar, a former graduate student of Strait's who is now a researcher at the University of New England in Australia, said in the release. "Then we find that A. sediba had an important limitation on its ability to bite powerfully; if it had bitten as hard as possible on its molar teeth using the full force of its chewing muscles, it would have dislocated its jaw."