A research published in 2012 got international attention as it suggested that a possible early human ancestor had lived on a diverse woodland diet, including hard foods mixed in

A research published in 2012 got international attention as it suggested that a possible early human ancestor had lived on a diverse woodland diet, including hard foods mixed in with tree bark, fruit, leaves and other plant products. South Africa’s Australopithecus sediba, discovered in 2008 at the archaeological site of Malapa in the Cradle of Humankind World Heritage Site, is again helping us to study and understand the origins of humans.

There however is a twist to this. A new research by an international team of researchers shows that Australopithecus sediba didn’t have the jaw and tooth structure necessary to exist on a steady diet of 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, said team leader David Strait, PhD, professor of anthropology in Arts & Sciences at Washington University in St. Louis.

Australopithecus sediba is thought by some researchers to lie near the ancestry of Homo, the group to which our species belongs, said Justin Ledogar, PhD, Strait’s former graduate student and now a researcher at the University of New England in Australia.

Professor Lee Berger had earlier said, I do truly believe that Australopithecus sediba will probably act as a Rosetta Stone, unlocking our understanding of where australopithecines went and where the earliest members of the genus Homo emerged.

It was added that 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.

The study published in the journal Nature Communications, describes biomechanical testing of a computer-based model of an Australopithecus sediba skull. The model is based on a fossil skull recovered in 2008 from Malapa, a cave near Johannesburg, South Africa.

Australopiths appear in the fossil record about four million years ago, and although they have some human traits like the ability to walk upright on two legs, most of them lack other characteristically human features like a large brain, flat faces with small jaws and teeth, and advanced tool-use.

Strait, a paleoanthropologist who has written about the ecological adaptations and evolutionary relationships of early humans, as well as the origin and evolution of bipedalism, said this study offers a good example of how the tools of engineering can be used to answer evolutionary questions. In this case, they help us to better understand what the facial skeleton can tell us about the diet and lifestyles of humans and other primates.

Examination of the microscopic damage on the surfaces of the teeth of A. sediba has led to the conclusion that the two individuals known from this species must have eaten hard foods shortly before they died. This gives us information about their feeding behavior. 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 bottom line, Strait said, is that the consumption of hard foods is very unlikely to have led natural selection to favor the evolution of a feeding system that was limited in its ability to bite powerfully. This means that the foods that were important to the survival of A. sediba probably could have been eaten relatively easily without high forces.