Functions and not just genetics influence the structure of jawbones in human populations, scientists at Johns Hopkins have found.
The researchers say these findings may be used to predict the diet of an ancient population, even if little evidence exists in the fossil record.
It can also make it easier for scientists to pinpoint the genetic relationship between fossils.
"Our research aimed to see how much of the mandible's-or jaw bone's-shape is plastic, a response to environmental influences, such as diet, and how much is genetic," stated Megan Holmes, graduate student at the Johns Hopkins Center for Functional Anatomy and Evolution, and lead author of the study.
"The idea that function influences the shape of jaw bones is great for the archeological record in terms of discovering the diet of a population, and it's also really useful for reconstructing the fossil record-finding which fossils are related to which, and how," he said.
The group chose to study the Arikara and Point Hope American Indian populations, since they were genetically isolated from other groups and ate different diets.
"The jaw bones were similar in children before they were old enough to start chewing, but different in adulthood, which implies that this divergence is likely a functional result of their diet and the use of their jaw, rather than genetics," stated Holmes.
The team was able to investigate very specific parts of the jaw bones and relate them to specific dietary habits. In the Point Hope population, for example, they found round, wide jaw bones-a result of having to exert more force to chew a harder diet.
The Arikara, on the other hand, did not show this expansion, which they attributed to the lighter chewing requirement of a softer diet.
Their results were published online June 23 in the American Journal of Physical Anthropology.