*Researchers Test Canine Tooth Strength for Clues to Behavior of Early
Human Ancestors*
**
*Measuring and testing the teeth of living primates could provide a
window into the behavior of the earliest human ancestors, based on their
fossilized remains. Research funded by the National Science Foundation
and led by University of Arkansas anthropologist Michael Plavcan takes
us one step closer to understanding the relationship between canine
teeth, body size and the lives of primates.
*
In an article published in American Journal of Physical Anthropology,
Plavcan and colleague Christopher B. Ruff of Johns Hopkins School of
Medicine report on an initial examination of the function of the shape
of canine teeth in primates. This is the first published comparative
analysis of canine strength for primates.

Understanding more about the function of canine teeth can lead to new
models for understanding human evolution. Plavcan has been studying
primate teeth and skulls for 24 years and spent four years collecting
dental data for this analysis.

The researchers compared the size, shape and strength of canine teeth
from 144 primates with similar measurements taken from 45 carnivores.
They examined the relationship of the size of primates’ canines to body
size and the relative strength of the teeth. This comparison could help
answer the speculation about the function of male primates’ canine teeth
in the competition for females. Are the canines used as weapons or
simply for display?

The reason we wanted to use the carnivores is that we know carnivores
use their canines for killing,” Plavcan said. “If primates’ canines are
too weak to function as weapons, then they’re all just for show.”

Among anthropoid primates, it is well known that the canine teeth of
males are up to four times as long as those of females. The researchers
compared the canine teeth of male and female primates.

If the male’s canines are stronger than the female’s canines that would
imply there is sexual selection for strength and that the tooth is
actually used as a weapon,” Plavcan said. Female’s canines are short,
and shorter, stubbier objects are harder to break. So, if the long, thin
male canines are as strong or stronger than those of the female, that
would also suggest they are capable of being used for fighting.”

The results were mixed in an interesting way.

We found that the primate canines are generally as strong as or stronger
than carnivore canines," Plavcan said. “But they are not associated with
any sort of estimate of sexual selection.

Generally the canines of males and females were equally strong. Given
that primates have such strong teeth in general, the researchers
suggested a couple of possible explanations. It could be that all
primate males have strong teeth because of a significant risk to
reproductive success for any male who breaks a canine tooth. Or it could
be that the strong teeth are due to basic inherited design.

Hominids the primate family that produced humans – retain body mass
sexual dimorphism; that is, males typically have a greater body mass
size than females. At the same time, the difference in size in canine
teeth between males and females is lost.

This goes back to the earliest hominids,” Plavcan said. In fact, one of
the few diagnostic characteristics of hominid evolution is reduction in
canine size dimorphism while maintaining strong body mass dimorphism.

For example, gorillas have chunky teeth set in massive bodies. To have
canines proportionately as long as other primates, a male gorilla’s
canines would have to be 25 centimeters long, and the teeth at the base
would then be too wide for his jaw.

This suggests that there may be an upper limit on canine size in
primates simply due to spatial constraints on fitting such teeth in the
jaws, the researchers wrote.

The difference in body size between male and female hominids has been
the subject of study because it is an obvious and important trait. Yet
there are drawbacks to using body size to understand sexual selection. A
change in body size can impact many other aspects of life, including
metabolism, feeding patterns and vulnerability to predators. Canine
teeth, on the other hand, are a far simpler system.

With canines, we can go in and effectively construct an experiment that
allows us to control for all these other variables and look at only one
thing,” Plavcan said. “The same phenomenon that works on the canines, we
can translate into the body mass and then into behavioral models for the
fossil record.

Source: University of Arkansas
http://www.physorg.com/news133709182.html
Thanx Robert. This is curious. the University of Arkansas? Well, the