In 2008, scientists recovered the skull of an Australopithecus sediba. This diminutive pre-human species that lived in southern Africa about 2 million years ago could be one of our ancestors or relatives. While research published in 2012 suggested its woodland diet consisted of hard foods, tree bark, fruit, leaves, and other plant products, new computer modeling of its jaw and teeth indicate that it couldn’t tackle such difficult foods—possibly affecting our evolutionary course.
“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,” said David Strait, PhD, professor of anthropology at Washington University in St. Louis. “Among other things, they were able to efficiently bite down on foods with very high forces.”
“Then we find that A. sediba had an important limitation on its ability to bite powerfully,” said Justin Ledogar, PhD, Strait’s former student and a researcher at the University of New England in Australia. “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.”
The researchers biomechanically tested a computer-based model of the skull found in 2008. The work resembled testing used by engineers to determine if planes, cars, machine parts, and other mechanical devices are strong enough to avoid breaking during use. While the research did not address whether A. sediba is one of our close evolutionary relatives, it did provide evidence that dietary changes shaped the evolutionary paths of early humans.
“Examination of the microscopic damage on the surfaces of the teeth of A. sediba has led to the conclusion that the 2 individuals known from this species must have eaten hard foods shortly before they died. This gives us information about their feeding behavior,” said Strait. “Yet, an ability to bite powerfully is needed in order to eat hard foods like nuts or seeds. This tells us that even though A. sediba may have been able to eat some hard foods, it is very unlikely to have been adapted to eat hard foods.”
The consumption of hard foods is very unlikely to have led natural selection for favor the evolution of a feeding system that was limited in its ability to bite powerfully, Strait said. As a result, the foods that were important to A. sediba’s survival could have been eaten relatively easily without high forces.
The study, “Mechanical Evidence That Australopithecus Sediba Was Limited in Its Ability to Eat Hard Foods,” was published by Nature Communications.