FROM SEED TO NUTS: HUMAN ANCESTOR'S FACE EVOLVED TO EAT SURVIVAL FOODS

TALLAHASSEE, Fla. -- The facial structure of an ancient relative of modern humans may have evolved to allow them to eat large, hard nuts and seeds as part of a survival strategy, according to a new study by an international team of researchers that includes Florida State University’s Dennis E. Slice.

The findings, published in the journal Proceedings of the National Academy of Science, challenge a long-standing hypothesis that the distinctive facial skeleton of Australopithecus africanus, a human relative who lived in Africa more than 2 million years ago, was a dietary adaptation for feeding on either small, hard objects or large volumes of food. The unique facial features included columns of bone positioned along either side of the nasal cavity that acted as struts to reinforce the face.

Using finite element analysis — an engineering technique used to examine how structures of complex design respond to external loads — as well as comparative, imaging and experimental methods, the team found that a small-object or high-volume diet was unlikely to explain the evolution of facial anatomy in this species. Instead, the team suggests that A. africanus might have used enlarged premolars, also known as bicuspids, and a structurally reinforced face to crack open and ingest large, hard nuts and seeds during periods when preferred, softer foods were in short supply.

“An interesting thing about these results is that they suggest an important role for relatively rare events in directing evolutionary change,” Slice said. “The overall structure of the Australopith face looks well-adapted to the sort of function we tested in our paper, but this is at odds with molar microwear patterns that suggest a varied diet of relatively few hard foods. It is possible that their facial architecture was driven not by their day-to-day activities but by their capacity to survive hard times by switching to what are called ‘fallback foods.’”

University at Albany anthropologist David Strait led the research team. Slice, an associate professor in Florida State’s Department of Scientific Computing, contributed to the design and analysis of the study and to the writing of the paper reporting the findings.

The paper, “The feeding biomechanics and dietary ecology of Australopithecus africanus,” appears in the Feb. 2 early edition of PNAS. To view the paper, visit www.pnas.org/content/early/2009/02/02/0808730106.abstract.

The research was made possible through grants from the National Science Foundation and the European Union.

Source: FSU Press Release - February 3, 2009