Study of Indian tribe illustrates that activity affects bone growth

Children need to exercise to build strong bones

Our bones change with our activity levels, says a University of Missouri-Columbia researcher. Therefore, it's important that we exercise to build strong bones, particularly as children.

"I like to think of bones as beams in a building," said Daniel Wescott, assistant professor of Anthropology. "Bone has to be strong enough to resist loads of weight, but you don't want to have too much bone, either. It changes in size and shape during your life. How it changes reflects what it does, and what you do."

Wescott and Deborah Cunningham, a graduate of MU and now a postdoctoral fellow at the Smithsonian Institute, studied the bones of Arikara Indians, a dominant tribe in North and South Dakota from the 14th to 19th centuries. Their study found that the bones changed as Arikaras' activities changed, providing the first physical evidence of the traditional male-females roles in the Arikara tribe. Historical accounts suggest Arikara women did all the farming, while men hunted, traded and fought in battles.

Wescott and Cunningham examined between 95 and 160 pairs of Arikara arm and leg bones from a period of four centuries. They found that female leg bones changed in morphology and asymmetry over time. Historical accounts indicate the Arikara began producing more crops during that period of change. Male leg bones did not show changes, but male arm bones did, probably because of increased use of firearms instead of bows and arrows.

"By the late 1700s, women's left legs showed signs of having borne greater loads. This probably reflects increases in the workload necessary to produce surplus crops. The Arikara were producing so much corn by the 1850s that they had fat surpluses they could use for trading," Wescott said. "The males didn't get involved in any horticulture in any way. I would say that they probably didn't even get involved with money from the crops. That was all the women's work."

Wescott said that bone changes also happen today. What we do is reflected in how our bones develop, which is why it's important to exercise to build strong bones, particularly during childhood.

"Exercising as a kid is the most important," Wescott said. "You can change the size and shape of your bones as an adult, but you really have to do strenuous work."

Wescott and Cunningham's study was published in July 2006 issue of the Journal of Archaeological Science.

Links:

Daniel Wescott
Department of Anthropology

Smithsonian Institution: National Museum of Natural History: Department of Anthropology

Mandan, Hidatsa, and Arikara Nation

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