Ancient "Nutcracker Man" really ate grass - d'oh!

Posted by Lydia Leavitt

For decades, scientists have been under the impression that the remains of Paranthropus boisei, a human from 2.3 to 1.2 million year ago, subsisted primarily on nuts mostly because of his hearty jaw and flat molar teeth.

But new research shows he actually munched on grass and sedges - a discovery that challenges traditional assumptions of early human diet habits.

By grinding a portion of the Nutcracker Man’s tooth, scientists were able to analyze the carbon isotope ratios to determine exactly what kind of food he ate. Carbon isotope ratios in tooth enamel reveals whether ancient animals ate plants that use C3 photosynthesis or C4 photosynthesis.

By grinding up a small portion of of the Paranthropus boisei’s tooth enamel and comparing it to 24 teeth from 22 other individuals who lived between 1.4 million and 1.9 million years ago, scientists were able to determine his diet compared to other evolutionary humans.

They found the Nutcracker Man’s diet was not really rich in C3 plant products, but rather C4 plants like grasses.

Carbon isotopes showed the 22 individuals tested had diets averaging 77 percent C4 plants such as grasses, ranging from a low of 61 percent to a high of 91 percent. That’s the same diet as other grazing animals that lived at the same time, the ancestors of the zebras, pigs, warthogs, and hippos, explained geochemist Thure Cerling.

Study co-author Kevin Uno, a University of Utah Ph.D. student in geology adds, "It was not competing for food with most other primates, who ate fruits, leaves and nuts; but with grazers - zebras' ancestors, suids [ancestors of pigs and warthogs] and hippos."

The significance of this discovery means these humans were competing not with other primates who ate fruits, leaves, and nuts, but rather with the grazing animals of that time. The new study also reveals that the species was eating grass and other C4 plants over a much longer period of time (from 1.4 million years and 1.9 million years) and in a much bigger geographic area (a 500 mile wide swath of East Africa) than previously believed.

Cerling also explained that scientists previously based many of their assumptions about the Nutcracker Man’s eating habits based on the size, shape, and wear of his teeth. Once the scientists analyzed the results with a drill, the results are completely different.

Perhaps it’s time for a new nickname?