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Science Forum Index » Archaeology Forum » Newswise article on the diet of Paranthropus boisei
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| Jack Linthicum |
 Posted: Thu May 01, 2008 7:27 am |
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Studies show that pre-humans such as Paranthropus boisei did not
necessarily have the diet that their pyhsiognomy suggests. Full study
cite below, pictures at cite for this article.
Findings Challenge Conventional Ideas on Evolution of Human Diet,
Natural Selection
Description
A University of Arkansas professor and his colleagues used a
combination of microscopy and fractal analysis to examine marks on the
teeth of members of an ancient human ancestor species and found that
what it actually ate does not correspond with the size and shape of
its teeth. This finding suggests that structure alone is not enough to
predict dietary preferences and that evolutionary adaptation for
eating may have been based on scarcity rather than on an animal’s
regular diet.
Image Gallery
Peter Ungar holds the skull of Australopithecus africanus, the first
hominin found in Africa.
Newswise — New findings suggest that the ancient human “cousin” known
as the “Nutcracker Man” wasn’t regularly eating anything like nuts
after all.
A University of Arkansas professor and his colleagues used a
combination of microscopy and fractal analysis to examine marks on the
teeth of members of an ancient human ancestor species and found that
what it actually ate does not correspond with the size and shape of
its teeth. This finding suggests that structure alone is not enough to
predict dietary preferences and that evolutionary adaptation for
eating may have been based on scarcity rather than on an animal’s
regular diet.
“These findings totally run counter to what people have been saying
for the last half a century,” said Peter Ungar, professor of
anthropology in the J. William Fulbright College of Arts and Sciences.
“We have to sit back and re-evaluate what we once thought.”
Ungar and his colleagues Frederick E. Grine of Cambridge University
and Stony Brook University and Mark F. Teaford of Johns Hopkins
University School of Medicine reported their findings in the PLoS ONE,
the online, open-access journal from the Public Library of Science.”
The researchers examined the teeth of Paranthropus boisei, an ancient
hominin that lived between 2.3 million and 1.2 million years ago and
is known popularly as the “Nutcracker Man” because it has the biggest,
flattest cheek teeth and the thickest enamel of any known hominin.
Since the first specimen was reported by Mary and Louis Leakey in
1959, scientists have believed that P. boisei fed on nuts and seeds or
roots and tubers found on the savannas throughout eastern Africa
because the teeth, cranium and mandible appear to be built for chewing
and crunching hard objects.
“The morphology suggests what P. boisei could eat, but not necessarily
what it did eat,” Ungar said.
Anthropologists have traditionally inferred the diet of this and other
ancient human ancestors by looking at the size and shape of the teeth
and jaws. However, by looking at the patterns of microscopic wear on a
tooth, scientists can get direct evidence for what these species
actually ate.
Ungar and his colleagues used a combination of a scanning confocal
microscope, engineering software and scale-sensitive fractal analysis
to create a microwear texture analysis of the molars of seven
specimens of P. boisei. The specimens spanned a time frame of almost a
million years and were found in Kenya, Tanzania and Ethiopia. Using
these techniques, they were able to create three-dimensional “point
clouds” that showed the pits and scratches on the teeth.
The researchers looked at complexity and directionality of wear
textures in the teeth they examined. Since food interacts with teeth,
it leaves behind telltale signs that can be measured. Hard, brittle
foods like nuts and seeds tend to lead to more complex tooth profiles,
while tough foods like leaves lead to more parallel scratches, which
corresponds with directionality.
They compared the dental microwear profiles of P. boisei to the
microwear profiles of modern-day primates that eat different types of
diets – grey-cheeked mangabeys and brown capuchins, which eat mostly
soft items but fall back on hard nuts or palm fronds, and the mantled
howling monkey and silvered leaf monkey, which eat mostly leaves and
other tough foods. They also compared the microwear analysis to
analyses of teeth from some of the fossil’s more contemporary
counterparts -- Australopithecus africanus, which lived between 3.3
million and 2.3 million years ago, and Paranthropus robustus, which
lived between 2 million and 1.5 million years ago.
The P. boisei teeth had light wear, suggesting that none of the
individuals ate extremely hard or tough foods in the days leading up
to death. It’s a pattern more consistent with modern-day fruit-eating
animals than with most modern-day primates.
“It looks more like they were eating Jell-o,” Ungar said.
This finding, while contradictory to previous speculation on the diet
of P. boisei, is in line with a paradox that has been documented in
fish. Liem’s Paradox states that animals may actively avoid eating the
very foods they have developed adaptations for when they can find
other food sources.
It appears that this paradox may hold true for P. boisei and for some
modern-day primates as well.
“If you give a gorilla a choice of eating a sugary fruit or a leaf, it
will take the fruit every time,” Ungar said. “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 finding represents a fundamental shift in the way researchers
look at the diets of these hominins.
“This challenges the fundamental assumptions of why such
specializations occur in nature,” Ungar said. “It shows that animals
can develop an extreme degree of specialization without the
specialized object becoming a preferred resource.”
This project was funded in part by grants from the National Science
Foundation. The researchers’ study is available at http://www.plosone.org/doi/pone.0002044
.
http://www.newswise.com/p/articles/view/540222/ |
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