A Penn State researcher is part of the team that developed techniques that have generated insights into dietary divergences between some of our human ancestors, allowing scientists to better understand the evolutionary path that led to the modern-day diets that humans consume.
"Our new techniques are allowing us to get beyond simple dichotomies and helping us understand the processes by which dietary evolution is working," said Peter Ungar, professor of anthropology at the University of Arkansas.
Ungar and Robert Scott, postdoctoral fellow at the University of Arkansas, with colleagues at the Worcester Polytechnic Institute, State University of New York at Stony Brook, Johns Hopkins University School of Medicine and Penn State University, report their findings in the August 4, 2005 issue of the journal Nature.
The researchers, including Dr. Alan Walker, Evan Pugh Professor of Biological Anthropology and Biology, Penn State, investigated microscopic wear on the teeth of two species of ancient hominims – Australopithecus africanus, which lived between 3.3 and 2.3 million years ago, and Paranthropus robustus, which lived between 2 and 1.5 million years ago. The pits and scratches found on the teeth offer a visual history of the type of food consumed by the tooth's owner. Pits indicate a diet of hard, brittle foods, like nuts and seeds, while scratches imply a diet of tough foods, like leaves and possibly meat.
Traditional examinations of these ancient teeth – counting pits and lines on a black and white electron micrograph image – suggested that A. africanus ate tough foods and P. robustus dined on hard, brittle fare. However, the researchers used a new technique developed by Ungar and his colleagues that combines engineering software, scale-sensitive fractal analysis and a scanning confocal microscope to create a reproducible texture analysis for teeth – and the analysis tells a more complete story.
The researchers looked at both roughness, or complexity, and directionality in the teeth they examined.
"Since food objects interact with teeth, we have different kinds of complexity in different diets. Directionality also correlates with diet," Scott said. Hard foods like nuts and seeds tend to lead to more complex tooth profiles, while tough foods like leaves lead to more scratches, which corresponds with directionality.