Our Ancient Cousin "Nutcracker Man" Actually Ate Like a Cow: Lots of Grass

By Patrick Morgan | May 3, 2011 1:21 pm

What’s the News: It turns out that the strong-jawed, big-toothed human relative colloquially known as “Nutcracker man” may never have tasted a nut. In a finding that questions traditional ideas of early hominid diet, researchers discovered that Paranthropus boisei, a hominid living in east Africa between 2.3 and 1.2 million years ago, mostly fed on grasses and sedges. “Frankly, we didn’t expect to find the primate equivalent of a cow dangling from a remote twig of our family tree,” researcher Matt Sponheimer told MSNBC.

How the Heck:

  • The researchers studied the early hominid’s diet by drilling off the enamel of 24 teeth from 22 different P. boisei specimens found in Kenya, ages ranging from 1.4 to 1.9 million years old.
  • The carbon isotopes in the pulverized enamel allowed them to look at diet because grasses and nuts have different carbon signatures: Nuts, as well as shrubs, herbs, and cool-season grasses, undergo a kind of photosynthesis known as C3 photosynthesis, which stores carbon-12, whereas sedges and tropical grasses undergo C4 photosynthesis, which stores carbon-13 in addition to carbon-12.
  • The carbon isotopes in these 24 P. boisei teeth revealed that 77% of their diet consisted of C4 plants like grass and papyrus, and that’s only an average percentage: The range was from 61 to 91% grasses and sedges.
  • Looking at the oxygen isotopes in the fossil teeth, the researchers also concluded that P. boisei lived in a “semi-arid savannah with woodlands along rivers or lakes.”

What’s the Context:

The Future Holds: This study calls into question the nut-eating habits of the genus Australopithecus too, so now researchers want to use the same technique to see if the isotopes measure up.

Reference: Thure E. Cerling et al. “Diet of Paranthropus boisei in the early Pleistocene of East Africa.” PNAS. doi: 10.1073/pnas.1104627108

Image: Melissa Lutz Blouin/University of Arkansas

CATEGORIZED UNDER: Human Origins, Living World
  • Anatomy Student


  • Dr. Scott Moody

    Nonsense that they digested like cows which are ruminants. Primates that are able to digest a lot of plant matter are hindgut fermenters so the analogy to be made is “ate like a horse.”

  • http://peicurmudgeon.wordpress.com/ peicurmudgeon

    They ate like cows and digested like horses.

  • Ubi Dubium

    My question to the researchers is: Would the seeds of C4 grasses leave the same carbon signature as the leafy parts? Can we tell whether P. Boisei was actually grazing versus eating mostly seeds? And is there some study that could be done to determine this?

  • http://philosophyofweightmanagement.blogspot.com/ fredt

    How do you distinguish between C4 direct from grass and C4 indirect via animals feeding on grass? We cannot do that in out lab.

  • fintin

    Wow. I ate grass for to try it when I was about 6, and it actually wasn’t as terrible as I thought. Now I know why.

  • casey

    I didn’t see in the article where it said they ‘digested like cows’. I think the comparison to cows was only in that they both ‘ate’ grass.

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    great magazine

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