Evolutionary Explanations of Eating Disorders
Igor Kardum, Asmir Gračanin, Jasna Hudek-Knežević
University of Rijeka, Faculty of Arts and Sciences Department of Psychology
This article reviews several most important evolutionary mechanisms that underlie eating disorders. The first part clarifies evolutionary foundations of mental disorders and various mechanisms leading to their development. In the second part selective pressures and evolved adaptations causing contemporary epidemic of obesity as well as differences in dietary regimes and life-style between modern humans and their ancestors are described. Concerning eating disorders, a number of current evolutionary explanations of anorexia nervosa are presented together with their main weaknesses. Evolutionary explanations of eating disorders based on the reproductive suppression hypothesis and its variants derived from kin selection theory and the model of parental manipulation were elaborated. The sexual competition hypothesis of eating disorder, adapted to flee famine hypothesis as well as explanation based on the concept of social attention holding power and the need to belonging were also explained. The importance of evolutionary theory in modern conceptualization and research of eating disorders is emphasized. Keywords: eating disorders, evolutionary theory, reproductive suppression, sexual competition
INTRODUCTION There is a disagreement among scientists about the basic definition of mental disorder, and usually discussions concerning its definition encompass the role of social values as well as the centrality and the necessity of the presence of failures in evolved adaptive mechanisms (Lilienfield & Marino, 1995; Wakefield, 1999, 2005). Evolutionary reasoning can help to discriminate between conditions of an
Igor Kardum, University of Rijeka, Faculty of Arts and Sciences, Department of Psychology, Slavka Krautzeka bb, 51000 Rijeka, Croatia. E-mail: email@example.com This paper is a part of research project Personality traits, emotional and social processes as determinants of health (009-0092660-2658), supported by the Croatian Ministry of Science, Education, and Sport. 247
PSYCHOLOGICAL TOPICS 17 (2008), 2, 247-263
organism that are the consequences of adaptive reactions designed by evolutionary processes and those that are the consequences of failures of these mechanisms, despite the fact that both kinds of conditions can be desired or undesired by an individual or society. Accordingly, mental disorders can be considered as conditions in which one or more psychological mechanisms do not compute according to the criteria that constitute their evolved function and in a way that is considered harmful (Cosmides & Tooby, 1999; Wakefield, 1999). This point of view is a base of the harmful dysfunction concept (Wakefield, 1999, 2005), with harmfulness being the only element included in the definitions of mental disorders given by the most scientists. Namely, concerning the evolved human traits, there is a question of whether a certain mechanism is operating in a way that produces the functional output it was designed to. It is well known that evolutionary processes result in three basic products: adaptations, which may be sometimes mulfunctional because of numerous reasons, by-products of adaptations, and evolutionary noise (Buss, Haselton, Shackelford, Bleske & Wakefield, 1998). Apart from malfunctioning of adaptive mechanisms, by-products and evolutionary noise may also in many cases be considered as pathology or described as abnormal, depending on the desired state of the individual. Adaptive mechanisms can produce painful and thus unwanted experiences even when triggered by the appropriate cues, and even when their intensity corresponds to their function. In addition, natural selection also results in the creation of other organisms...