By Audrey Huang
Johns Hopkins Medicine

Careful analysis of microscopic abrasions on the teeth of early human "cousins" by researchers at Johns Hopkins, University of Arkansas, University of Cambridge and Stony Brook University show that although equipped with thick enamel, large jaws and powerful chewing muscles, this ancient species may not have eaten the nuts, seeds or roots their anatomy suggests. Instead, the tooth wear suggests a more general diet, as reported April 30 in Public Library of Science One.

"For so many years we've operated under the assumption that the shape of something's teeth, jaws and skull tells us what they habitually ate," said Mark Teaford, a professor of anatomy at Johns Hopkins' Center for Functional Anatomy and Evolution. "But it seems like we had the wrong idea. Just because they're capable of eating hard foods doesn't mean that they did. It really makes us rethink some of our basic assumptions."

Using high-powered microscopy to scan tooth surfaces, and computer programs that measure imperfections on the surfaces of teeth, the researchers analyzed tooth surfaces from Paranthropus boisei from eastern Africa. According to most researchers, P. boisei's jaw and tooth structure was so specialized and extreme it must have had a very specialized diet. In fact, its anatomy gave it the nickname "Nutcracker Man."

Measuring the microwear from permanent molars of P. boisei from Ethiopia, Kenya and Tanzania dating from 2.27 million years ago to about 1.4 million years ago, the team compared its results with microwear from living primates and other fossils. The researchers found that P. boisei teeth had very little pitting indicative of eating hard foods.

"It seems that while they were perhaps capable of eating harder foods, they generally didn't," Teaford said. "We see similar situations in modern primates, who often like soft fruit. But they can't find that all the time, so occasionally they'll eat harder or tougher foods if they have to."

"Looking at P. boisei, you think, 'Wow, it's a chewing machine,' but that's really an oversimplification. It may not have been so specialized," he said.

The research was funded by the National Science Foundation.

Authors on the paper are Peter Ungar, of the University of Arkansas; Frederick Grine, of Stony Brook University and the University of Cambridge; and Teaford of Johns Hopkins.

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