Shan Guisinger, Ph.D

David Schuldberg, Ph.D.

The University of Montana– Missoula

Growing genetic evidence indicates that symptoms of anorexia nervosa (AN), representing illness today, were selected in the past. Eight genes have been identified in AN individuals that decrease appetite and increase activity, triggered by falling weight. The adapted-to-flee-famine hypothesis (Affh) has proposed that abilities to ignore hunger, deny starvation, and move energetically are remnants of archaic adaptations that helped some in starving hunter-gatherer bands lead others from depleted home range. Yet, only 1-2% carrying the genes develop the disorder, which also exhibits sex differences. Maynard Smith clarified when natural selection results in stable polymorphisms; density-dependent selection describes how net individual benefit depends on behavioral strategies of others. We model effects of a variety of variables — including number of potential leaders, survival of those leaving home, refeeding success, reproductive outcomes for “successful” anorectics, and syndrome lethality — evaluating effects on the prevalence and sex distribution of AN.