After a half-century of referring to an ancient pre-human as "Nutcracker Man" because of his large teeth and powerful jaw, scientists now conclude that he actually chewed grasses instead. The study "reminds us that in paleontology, things are not always as they seem," commented Peter S. Ungar, chairman of anthropology at the University of Arkansas.
The new report, by Thure E. Cerling of the University of Utah and colleagues, is published in Tuesday's edition of Proceedings of the National Academy of Sciences.
Cerling's team analyzed the carbon in the enamel of 24 teeth from 22 individuals who lived in East Africa between 1.4 million and 1.9 million years ago. One type of carbon is produced from tree leaves, nuts and fruit, another from grasses and grasslike plants called sedges.
It turns out that the early human known as Paranthropus boisei did not eat nuts but dined more heavily on grasses than any other human ancestor or human relative studied to date. Only an extinct species of grass-eating baboon ate more, they said.
"That was not at all what we were expecting," Cerling said in a telephone interview. Scientists will need to rethink the ways our ancient relatives were using resources, he said.
Added co-author Matt Sponheimer of the University of Colorado: "Frankly, we didn't expect to find the primate equivalent of a cow dangling from a remote twig of our family tree."
The skull of Paranthropus was discovered by Mary and Louis Leakey in 1959 at Olduvai Gorge in Tanzania, and helped put the Leakeys on the world stage. Their daughter-in-law, Maeve Leakey, is a co-author of the paper.
Cerling said much of the previous work on Nutcracker Man was based on the size, shape and wear of the teeth. His team analyzed bits of tooth removed with a drill and the results were completely different, Cerling said.
"It stands to reason that other conclusions about other species also will require revisions," he said.
Ungar, who was not part of the research team, suggested in 2007 the possibility that Nutcracker Man human ate grasses, based on tooth wear.
"The big, flat molars, heavily buttressed skull, and large, powerful chewing muscles of Paranthropus boisei scream `nut cracker,' and that is exactly what this species has been called for more than half a century," he said via email. "But science demands that our interpretations be tested."
With carbon analysis, the researchers take us "one step closer to understanding the diets of these fascinating hominins," Ungar said.
"This is a very important paper ... because people have traditionally felt that the teeth of boisei were incapable of processing foods like grasses," added biology professor Mark Teaford of Johns Hopkins University.
Cerling said it took some convincing to get the tooth samples for drilling from the National Museum of Kenya. "The sound of the drill may make a lot of paleontologists and museum staff cringe," co-author Kevin Uno, a doctoral student at Utah, said in a statement. But "it provides new information that we can't get at any other way."
The study was funded by the National Science Foundation and the University of Colorado.