For Those Who Eat Steak And Beans: When There Is No Steak, You Eat The Beans

According to a study published in the open-access journal PLoS
ONE, the ancient human ancestor species Paranthropus
boisei did not actually eat the type of food that is
suggested by the size and shape of its teeth. Professor of anthropology
Peter Ungar (J. William Fulbright College of Arts and Sciences,
University of Arkansas) and colleagues used microscopy and
fractal analysis to analyze tooth marks on the ancient species. Their
findings indicate that structure alone is not sufficient to determine
what predecessors ate, and evolution could have dictated eating
adaptations based on scarcity instead of
on an animal's regular diet.



Ungar stated that, "These findings totally run counter to what people
have been saying for
the last half a century. We have to
sit back and re-evaluate what we once thought."



Paranthropus boisei was an ancient hominin from
between 2.3 million and 1.2 million
years ago. He is known as the "Nutcracker Man" due to bigger
and flatter cheek teeth and thicker enamel than any known hominin.
Since 1959 when Mary and
Louis Leakey wrote about the first specimen, it was believed that the
hominin ate nuts, seeds, roots, and tubers that could be found on the
savannas in eastern Africa. P. boisei had
the teeth, cranium, and mandible that were seemingly designed to chew
and crunch hard objects. "The morphology suggests what P.
boisei could eat, but not necessarily what it did
eat," Ungar said.



Usually, anthropologists analyze the size and shape of
the teeth and jaws of human ancestors to determine what it ate. A
microscopic investigation of the wear and tear on the tooth, however,
can help researchers determine what the species actually ate. Ungar and
his colleagues created a microwear texture analysis - 3-dimensional
"point
clouds" that show pits and scratches on the teeth - of the molars of
seven specimens of P. boisei. Spanning a time frame
of about 1,000,000 years, the specimens came from Kenya, Tanzania and
Ethiopia.



Teeth were analyzed with respect to their complexity and directionality
of wear texture - nuts, seeds, and other hard and brittle foods leave
more complex tooth profiles and tough foods like leaves leave parallel
scratches. Ungar and colleagues compared the dental microwear profiles
of P. boisei to those of primates living today such
as: grey-cheeked mangabeys and brown capuchins (that eat mostly soft
items but can eat hard nuts or palm fronds in hard times) and the
mantled howling monkey and silvered leaf monkey (that eat mostly leaves
and other tough foods). In addition, the researchers compared P.
boisei to contemporary hominids such as Australopithecus
africanus (living from 3.3 million to 2.3 million years ago)
and Paranthropus robustus (living from 2 million to
1.5 million years ago).



Finding that the P. boisei specimens had light
wear, the researchers concluded that none of the individuals probably
ate very hard or tough foods in the last days of their lives. The
pattern is actually more similar to what is found in modern-day
fruit-eating animals rather than in most modern-day primates. "It looks
more like they were eating Jell-o," stated Ungar to highlight how this
evidence contradicts what scientists previously thought that the
species ate.



"If you give a gorilla a choice of eating a sugary fruit or a leaf,
it will take the fruit every time," said Ungar. "But if you
look at a gorilla's skull, its sharp teeth are adapted to consuming
tough leaves. They don't eat the leaves unless they have to."



"This challenges the fundamental assumptions of why such
specializations occur in nature," concluded Ungar. "It shows
that animals can develop an extreme degree of specialization without
the specialized object becoming a preferred resource."



Dental Microwear and Diet of the Plio-Pleistocene Hominin
Paranthropus boisei

Ungar PS, Grine FE, Teaford MF

PLoS ONE (2008). 3(4): e2044.

doi:10.1371/journal.pone.0002044

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Here to View Article



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Written by: Peter M Crosta