University of Utah scientists improved a method of testing fossil teeth, and showed that early human relatives varied their diets with the seasons 1.8 million years ago, eating leaves and fruit when available in addition to seeds, roots, tubers and perhaps grazing animals.

"By analyzing tooth enamel, we found that they ate lots of different things, and what they ate changed during the year," says University of Utah geology doctoral student Ben Passey, a coauthor of the study in the Friday, Nov. 10 issue of the journal Science.

"We wanted to know if they had variability in their diets on the time scale of a few months to a few years," he says. "The new method showed that their diets were extremely variable. One possibility is that they were migrating seasonally between more forested habitats to more open, savanna habitats."

Study coauthor and geochemist Thure Cerling a University of Utah distinguished professor of geology and biology says the study of the now-extinct, ape-like species known as Paranthropus robustus is important because it "shows that the variability in human diet has been 'in the family' for a very long time. It is this variability that allows modern humans to utilize foods from all over the world."

The researchers used a laser to remove tiny samples from four 1.8-million-year-old fossilized Paranthropus teeth, then tested the samples to determine the ratios of two isotopes or forms of carbon.

Plants fall into two broad classes depending on the way in which they use photosynthesis to convert sunlight, water and carbon dioxide into plant matter and oxygen. Carbon isotope ratios reveal the extent to which the relatives of early humans ate so-called C3 plants, which include fruit and leaves from trees in both the forest and savanna, and C4 plants, which grow mostly on the savanna and include potato-like tubers, grasses, and seeds and roots from grasses. If the early hominids ate meat from gras
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Contact: Lee Siegel
leesiegel@ucomm.utah.edu
801-581-8993
University of Utah
9-Nov-2006