Androgen Receptor Gene Polymorphism, Aggression, and Reproduction in Tanzanian Foragers and Pastoralists

August Androgen Receptor Gene Polymorphism, Aggression, and Reproduction in Tanzanian Foragers and Pastoralists Marina L. Butovskaya 0 1 Oleg E. Lazebny 0 1 Vasiliy A. Vasilyev 0 1 Daria A. Dronova 0 1 Dmitri V. Karelin 0 1 Audax Z. P. Mabulla 0 1 Dmitri V. Shibalev 0 1 Todd K. Shackelford 0 1 Bernhard Fink 0 1 Alexey P. Ryskov 0 1 0 1 Department of Cross-Cultural Psychology and Human Ethology, Institute of Ethnology and Anthropology, Russian Academy of Sciences , Moscow , Russia , 2 Department of Evolutionary and Developmental Genetics, Koltzov Institute of Developmental Biology, Russian Academy of Sciences , Moscow , Russia , 3 Department of Genome Organization, Institute of Gene Biology, Russian Academy of Sciences , Moscow , Russia , 4 Biological Faculty, Moscow State University , Moscow , Russia , 5 Department of Archaeology, College of Arts and Social Sciences, University of Dar es Salaam, Dar es Salaam, Tanzania, 6 Department of Psychology, Oakland University , Rochester, Michigan , United States of America, 7 Institute of Psychology, University of Göttingen , Göttingen , Germany 1 Editor: Andrew C. Gallup, State University of New York at Oneonta, UNITED STATES The androgen receptor (AR) gene polymorphism in humans is linked to aggression and may also be linked to reproduction. Here we report associations between AR gene polymorphism and aggression and reproduction in two small-scale societies in northern Tanzania (Africa)-the Hadza (monogamous foragers) and the Datoga (polygynous pastoralists). We secured self-reports of aggression and assessed genetic polymorphism of the number of CAG repeats for the AR gene for 210 Hadza men and 229 Datoga men (aged 17-70 years). We conducted structural equation modeling to identify links between AR gene polymorphism, aggression, and number of children born, and included age and ethnicity as covariates. Fewer AR CAG repeats predicted greater aggression, and Datoga men reported more aggression than did Hadza men. In addition, aggression mediated the identified negative relationship between CAG repeats and number of children born. - Funding: This work was supported by the Russian Foundation for Humanities—12-01-00032—MLB, the Russian Foundation for Basic Research—13-0600393—MLB, the Russian Foundation for Basic Research—12-04-31869—APR, the Russian Foundation for Basic Research—13-04-00858—APR, the Research Program of Russian Academy of Sciences 'Molecular and Cell Biology'—APR, the President RF Program—5233.2012.4—APR, and the President RF Program—2501.2014.4—APR. The Aggression in traditional and modern societies is sometimes deployed to acquire resources and, therefore, social status and reproductive opportunities [1–6]. Even in forager societies with marked egalitarianism, aggressive competition between men for access to women is substantial, with most homicides attributable to competition between men [7,8–11]. Differences in mating systems may account for some of the variation in aggression. In hunter-gatherer societies, such as the monogamous Hadza of Tanzania (Africa), men invest more in offspring than in small-scale pastoralist societies, such as the polygynous Datoga of Tanzania [12–14]. Polygyny and between-group aggression redirect men’s efforts from childcare toward investment in Competing Interests: The authors have declared that no competing interests exist. male-male relationships and the pursuit of additional mates [15]. When men participate in childcare, their testosterone (T) level decreases [15–18]. Muller et al. [19] found that, among the monogamous, high paternally investing Hadza, T levels were lower for fathers than for non-fathers. This effect was not observed among the polygynous, low paternally investing Datoga. These results were interpreted as corroborating the ‘challenge hypothesis’ [20], which posits that T facilitates reproductive effort, including investment in mate-seeking, at the expense of parenting effort. According to the challenge hypothesis, T promotes aggression when this is beneficial for reproduction, as it is, for example, in combat with rivals over access to women. The effect of androgens, such as T, operates through stimulation of androgen receptors [21– 23]. The androgen receptor (AR) gene contains a polymorphic and functional locus in exon 1, comprising two triplets (CAG and GGN). This locus supports a regulatory function that responds to T, with fewer CAG repeat clusters being more effective in transmitting the T signal [22]. Moreover, the length of the GGN repeat predicts circulating and free T in men [23]. These relationships have inspired research investigating associations of the AR gene polymorphism with personality traits and behavioral correlates, including antisocial behavior and aggression [24]. The results of these studies are equivocal. Some studies report an effect of CAG and GGN polymorphisms on impulsive personality traits [25,26] and violence [27], whereas other studies do not find links between (...truncated)