Johns Hopkins Logo It seems intriguing to know that external factors may influence jaw shape. As per scientists at Johns Hopkins, dietary factors apparently play a role in structuring of the jaw bone apart from genetics. These outcomes may indicate the diet of individuals in early life.

As a part of the study, the Arikara and Point Hope American Indian populations were scrutinized as they come from different genetic backgrounds and consume different diets. The investigators examined bones from the 1600s to 1700s and observed diet records too. People from Point Hope in Alaska seemed to consume a hard diet constituting rough dried meat. They also stripped leather using their teeth. On the other hand, people from Arikara in the Dakota region of the United States, consumed a lighter diet along with farming and little hunting.

“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. We used archaeological jaw bones from two different regions to answer that question. Before we can make inferences about what the shape of a bone tells us, like what environment the individual lived in, who it’s related to or what it ate, we have to understand what creates that shape. 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,” elaborated Megan Holmes, graduate student at the Johns Hopkins Center for Functional Anatomy and Evolution, and lead author of the paper.

Jaw bones of 63 individuals from Point Hope and 42 persons from Arikara were observed using an X-ray gun and calipers. The scientists used the measurements to generalize the sizing of the complete jaw. They also found that the shape of the jaw during childhood was similar till the chewing process started. It also presumably changed during adulthood which suggests that this difference is a result of their diet and ways of using the jaw other than genetics.

This inference was drawn from an engineering connotation that says that the stress applied to a bone influences its shape. The analysts disclosed specific dietary habits associated with particular jaw shapes. The Point Hope Population apparently had round and wide jaw bones owing to more pressure applied while chewing hard substances. Contrarily, people from Arikara did not have wide jaws since they consumed a soft diet that necessitated less force for chewing.

Lead author Holmes concludes that though genetics create a blueprint of the bone, many extrinsic variables affect its overall construction. Mechanical force from muscle stress and strain from routine activities can restructure the bone, both at the surface and internally. Precise measurements stating how much of the mandible if linked to diet and genomes will help scientists comprehend the origin clearly.

The findings are published in the June 23issue of the American Journal of Physical Anthropology.