The strong-jawed
human relative nicknamed "Nutcracker Man"
likely didn't crack nuts at all, preferring to
graze on grass like a cow instead, scientists find.
These findings could dramatically alter
conventional wisdom regarding what the earliest members of the human
lineage and their relatives ate.
The extinct hominid,
officially called Paranthropus boisei,
ranged across East Africa 1.2 million to 2.3
million years ago, living side-by-side with the direct ancestors of
humanity. It earned its nickname because of its
massive jaw and huge molars.
Now scientists
investigating carbon isotope ratios in Nutcracker Man's teeth found
"it most likely was
eating grass, and most definitely was not cracking nuts,"
Cerling said.
"Frankly, we didn't
expect to find the primate equivalent of a cow
dangling from a remote twig of our family tree,"
said researcher Matt Sponheimer at the University of Colorado
at Boulder.
By looking at the carbon isotope ratios in
tooth enamel, scientists can decipher the past diet. The
method relies on the type of carbon used in photosynthesis, the
process in which carbon dioxide and water, with energy from the sun,
are turned into food for certain plants. For instance, trees and the
leaves, nuts and fruits they produce, as well as shrubs, herbs and
cool-season grasses, all rely on C3 photosynthesis, which prefers
carbon-12, while tropical grasses and sedges such as papyrus rely on
C4 photosynthesis, where both carbon-12 and the heavier carbon-13
isotope are used.
The scientists found
that P. boisei did not eat nuts or other C3 items,
but chewed more heavily on grasses than any
early human, human ancestor or human relative studied to date. Their
rugged jaws may have helped them munch on tough grass.
"We have been
looking at this organism through the wrong lens,
which may have led to significant distortions
in our understanding of its biology, ecology and evolution,"
Sponheimer told LiveScience.
Approximately 2.5
million years ago, researchers
suggest the australopithecines split into the genus
Homo, which produced our species, and the genus
Paranthropus, which dead-ended. So what led Paranthropus
to die off? It could have been direct
competition with Homo, which grew more skilled in tool use
over time, or it could have been a variety
of other factors, including having a slower reproductive rate,
Sponheimer said.
