Eat Nuts.. or.. Grass? Huh?

Thure E. Cerling, Emma Mbua, Francis M. Kirera, Fredrick Kyalo Manthi, Frederick E. Grine, Meave G. Leakey, Matt Sponheimer, and Kevin T. Uno

Diet of Paranthropus boisei in the early Pleistocene of East Africa
PNAS 2011 ; published ahead of print May 2, 2011, doi:10.1073/pnas.1104627108


The East African hominin Paranthropus boisei was characterized by
a suite of craniodental features that have been widely interpreted
as adaptations to a diet that consisted of hard objects that required
powerful peak masticatory loads. These morphological adaptations
represent the culmination of an evolutionary trend that
began in earlier taxa such as Australopithecus afarensis, and presumably
facilitated utilization of open habitats in the Plio-Pleistocene.
Here, we use stable isotopes to show that P. boisei had a diet
that was dominated by C4 biomass such as grasses or sedges. Its
diet included more C4 biomass than any other hominin studied
to date, including its congener Paranthropus robustus from South
Africa. These results, coupled with recent evidence from dental
microwear, may indicate that the remarkable craniodental morphology
of this taxon represents an adaptation for processing
large quantities of low-quality vegetation rather than hard objects.