Researchers from Johns Hopkins, the University of Arkansas, Worcester Polytechnic Institute and other institutes have come together to develop a new way to examine the fossils of our ancestors' teeth to predict how our diets have evolved through the ages and why.
By comparing teeth from two species of early humans, Australopithecus africanus and Paranthropus robustus, the researchers confirm previous evidence that A. africanus ate more tough foods, such as leaves, and P. robustus ate more hard, brittle foods. But they also revealed wear patterns suggesting that both species had variable diets. This new information implies that early humans evolved and altered their diet according to seasonal and other changes in order to survive said the researchers.
The new approach to studying dental microwear, the microscopic pits and scratches on the tooth surface caused by use, offers a more accurate measurement of the surface's appearance and is described in the August 4 issue of Nature.
A team of scientists from the University of Arkansas and Worcester Polytechnic Institute developed the software, called "scale-sensitive fractal analysis," to analyze fossilized tooth surfaces through a confocal microscope, which allows three-dimensional analysis of an object. The specimen is put in and the microscope is programmed to step down at fine intervals, perform its series of scans, and collect 3D coordinates for each data point. The result is like a map of the earth that shows mountains, valleys and plains in full relief, only at a microscopic scale.
As anticipated from traditional examination of fossilized teeth, the tooth surfaces of P. robustus were more pitted and complex, while those of A. africanus were more scratched, with features often running in more uniform directions. The study also revealed unexpected variability in the samples for each species and overlapping data for the two species. The researchers say this suggests that both species relied on their less preferred foods during periods of food scarcity.