Sex Differences in Same-Sex Aggression

Abstract

With few exceptions, males tend to exhibit higher 8 levels of aggressive behaviors than females. This 9 sex difference reflects differences in evolution-10 arily adaptive reproductive strategies based on 11 mating versus parenting trade-offs, with males 12 competing to maximize sexual access to females. 13 199 actually survive to reproduce at all. As if the 200 competition was not enough for males, female 201 elephant seals deliberately attempt to mate with 202 the most socially dominant and "protest" against 203 the advances of subordinate males. This further 204 increases male-male conflict and allows females 205 to effectively choose the best mates. Physical size 206 in the elephant seal thus allows males to compete 207 while simultaneously acting as a signal of quality 208 to females, increasing the likelihood that the larg-209 est males reproduce and increase their overall 210 fitness. Sexually dimorphic traits have evolved 211 in hominid species also, such as facial hair, voice 212 pitch, and physical size, and likely evolved as a 213 result of inter-and intrasexual selection (Archer 214 2009). Furthermore, archaeological evidence sug-215 gests that aggression can increase male fitness 216 benefits (Grauer and Stuart-Macadam 1998). 217 From the principles of sexual selection and 218 parental investment theory, testable hypotheses 219 regarding the expression of behaviors or traits 220 can be generated. In the case of aggression, the 221 following predictions can be made: 222 235 development, reach its zenith during the most 236 reproductive phase of the lifespan, and decline 237 with increasing age. 238 6. In our evolutionary past, males who use 239 aggression successfully should achieve fitness 240 gains.