‘Jaws of steel’ helped primitive man crack hard nuts, seeds

February 4th, 2009 - 3:44 pm ICT by IANS  

Washington, Feb 4 (IANS) Our ancestors, going back 2.5 million years, had jaws of steel with which they cracked open hard nuts and objects, unlike human species today with much more delicate and smaller teeth, a research study has shown.Mark Spencer, Arizona State University (ASU) assistant professor and evolutionary scientist, and doctoral student Caitlin Schrein used futuristic computer modelling and simulation technology to build a virtual model of the A. africanus skull to see how the jaw operated.

“We started with a CT scan of a skull that is one of the most complete specimens of A. africanus that we have,” said Spencer, lead investigator of the study funded by the National Science Foundation and the European Union.

This would be a later ancestor of Lucy - STS5 - who is affectionately known as “Mrs. Ples.” The skull, discovered in 1947, has struts on the side of the nose, but no teeth. “We meshed those data with another specimen with teeth to make the virtual model of the bone and tooth structure.

“Then we looked at chimpanzees, who share common features with Australopithecus, and took measurements of how their muscles work and added that to the model. We were able to validate this model by comparing it to a similar model built for a species of monkey called macaques,” Spencer explained.

The result - a rainbow coloured virtual skull that illustrates forces absorbed by the cranial structure in simulated bite scenarios and how their unusual facial features were ideally suited to support the heavy loads of cracking hard nuts.

“The enlargement of the premolars, the heavy tooth enamel and the evidence now that they were loading forcefully on the molars suggest the size of the objects were larger than the previously hypothesized small seeds and nuts,” said Spencer.

“These fall-back foods - hard nuts and seeds - were important survival strategies during a period of changing climates and food scarcity,” he added, according to an ASU release.

These findings were published in the February issue of Proceedings of the National Academy of Sciences.

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