Passey, who is working on his Ph.D. degree, "really made terrific advances in the lab to make this [study] possible," Cerling says.
The laser was used to remove samples at various points along the length of the tooth, which is marked by tiny ridges called perikymata. They run parallel to the tooth's crown and represent tooth growth, similar to tree rings. Perikymata are produced under the gums during the animal's juvenile years, when teeth are growing.
Each laser sampling vaporized enamel that formed during several months and thus represented what Paranthropus ate during that period. By taking several samples off the length of each tooth, the researchers reconstructed a few years of each creature's diet.
When the laser is used, the vaporized enamel is confined within a cylindrical chamber a few inches long. Carbon from carbonate in tooth enamel combines with oxygen to produce carbon dioxide gas, which then is analyzed by the mass spectrometer.
Your Teeth are What You Eat
If the sample has a relatively high ratio of carbon-13 to carbon-12, it means the early human relative was eating a diet rich in C4 plants most commonly found on the African savanna, such as seeds and roots from grasses, and grass-like plants called sedges, which include tubers. They also may have eaten animals that grazed on C4 plants.
If a sample has a relatively low ratio of carbon-13 to carbon-12, it means Paranthropus was eating C3 plants, including the leaves and fruits of trees and shrubs, as well as forbs, which are broadleaf herbs that are not grasses. Forests contain almost entirely C3 plants. African savanna has both C3 and C4 plants.
Analyses of the Paranthropus teeth revealed that the early human relatives had diets that varied in the proportion of C3 and C4 plants both seasonally and from year to year. The year-to-year variation in
Source:University of Utah