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Dominating versus eliminating the competition: Sex differences in human intrasexual aggression

Published online by Cambridge University Press:  20 August 2009

Joyce F. Benenson
Joyce F. Benenson
Affiliation:
Department of Psychology, Emmanuel College, Boston, MA 02115; Department of Biological Anthropology, Harvard University, Cambridge, MA 02138. Joyce.Benenson@gmail.com
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Abstract

Archer presents a traditional view of intrasexual competition. Knowledge of a species' social structure provides a more complete picture. Human males compete against individuals with whom they may cooperate later in inter-group aggression. By contrast, females compete against individuals for a mate's continued support. Females' aggression may aim at eliminating the competition, whereas males simply may attempt to dominate others.

Type
Open Peer Commentary
Information
Behavioral and Brain Sciences , Volume 32 , Issue 3-4 , August 2009 , pp. 268 - 269
Copyright
Copyright © Cambridge University Press 2009

Archer argues that across most species, males' greater intrasexual competition for mates accounts for their higher rates of aggression, with variation in paternal care elucidating the magnitude of the sex difference. Defining intrasexual competition as including not only mating contests but also breeding competition, however, provides a broader perspective (Clutton-Brock Reference Clutton-Brock2007; Reference Clutton-Brock2009). Breeding competition may include contests over food, territory, helpers, protection, and status, as well as other factors that enhance reproductive success within a particular ecology. A species' social structure determines in part how these challenges are confronted, through delineating patterns of same-sex associations, asymmetries in sex-biased investment in both kin and non-kin, and functions of same-sex alliances and coalitions (Wrangham Reference Wrangham, Smuts, Cheney, Seyfarth, Wrangham and Struhsaker1987). To understand more completely human sex differences in patterns of aggression, Archer could reach beyond consideration of the benefits and costs of physical fighting to incorporate an understanding of a species' social structure.

Humans segregate themselves by sex early in the juvenile period (Maccoby Reference Maccoby1988). Across varied cultures beginning in middle childhood and continuing into adulthood, human males interact in large, loosely structured, interconnected same-sex groups, whereas human females interact with one same-sex individual at a time (Benenson et al. Reference Benenson, Apostoleris and Parnass1997; Cairns et al. Reference Cairns, Xie, Leung, Bukowski and Cillessen1998; Markovits et al. Reference Markovits, Benenson and Dolenszky2001; Reference Markovits, Benenson and White2006; Savin-Williams Reference Savin-Williams, Foot, Chapman and Smith1980). Additionally, human males invest more than females in, and exhibit more tolerance towards, same-sex peers (Benenson et al. Reference Benenson, Morganstein and Roy1998; Reference Benenson, Saelen, Markovits and McCabe2008b; Reference Benenson, Markovits, Fitzgerald, Geoffroy, Fleming, Kahlenberg and Wrangham2009). Sex differences in group versus individual investment extend to sexual partners. Like polygynously and monogamously mated primates, human females typically form a long-term bond to one sexual partner, whereas human males more frequently form bonds with multiple short- and long-term sexual partners.

Unique facets of humans' social structure should influence Archer's conclusions regarding sex differences in aggression. More than in most other species, human females rely heavily on the investment of one mate to provision and protect themselves and their offspring (Lancaster & Lancaster Reference Lancaster, Lancaster and Ortner1983). Consequently, in contrast to other species, human females invest more in a mate to the exclusion of other individuals.

Likewise, unlike males in virtually all primate species (with the exception of chimpanzees, Pan troglodytes), human males routinely engage in lethal coalitionary inter-group contests (LeBlanc & Register Reference LeBlanc and Register2003; Wrangham Reference Wrangham1999). Success in these contests heavily influences the survival and reproductive fitness of the entire community. Like male chimpanzees, human males therefore must balance intra-group competition for status and mates with cooperation with these same competitors during inter-group contests. Heavy investment in male peers combined with high tolerance for transgressions likely produce rapid reconciliation of within group conflicts during inter-group contests.

By their nature, groups enhance competitive and aggressive behaviors, whereas one-on-one competition disguises competition with more placating behaviors, including signals of anxiety and depression – for both sexes (Bales & Borgatta Reference Bales, Borgatta, Hare, Borgatta and Bales1955; Benenson et al. Reference Benenson, Nicholson, Waite, Roy and Simpson2001; Reference Benenson, Maiese, Dolenszky, Dolensky, Sinclair and Simpson2002). Groups enhance competition because fewer resources are available per individual and many individuals vie for rank. Because human males must maintain a group's integrity given the perpetual threat of inter-group contests, however, group members likely dampen competitions' adverse effects by providing mediators, allies, and alternate partners, and promoting loyalty to the larger group. A human male's goal in intrasexual competition consequently becomes to dominate other individuals within the group without harming the group's integrity. Within-group fighting then may be less important than between-group fighting in explaining sex differences.

Human females' competition occurs within a different structure. Isolated one-on-one competition without the support that a group provides jeopardizes the relationship's survival. Human females' same-sex dyadic relationships endure for shorter periods than those of males, most likely because of their lesser ability to resolve conflicts (Benenson & Christakos Reference Benenson and Christakos2003).

A human female must compete, however, not only to initiate a long-term bond with a high status mate who can enhance the survival and status of her offspring, but also to maintain her mate's loyalty. She must fend off competitors for her mate's resources and protection, or in the case of polygynous unions, for a greater share of her mate's investment.

Social exclusion of competitors provides the perfect mechanism. Because females' same-sex relationships by their nature are not interconnected or group-based, exclusion of another female can occur seamlessly. Feshbach showed that compared to their male peers, females in both early childhood (Feshbach Reference Feshbach1969) and adolescence (Feshbach & Sones Reference Feshbach and Sones1971) were less welcoming to a same-sex newcomer. Likewise, in an experiment with limited resources, 4-year-old female triads were more likely than male triads to exclude the one child who obtained a resource, whereas males competed individually for the resource while maintaining the integrity of the trio (Benenson et al. Reference Benenson, Antonellis, Cotton, Noddin and Campbell2008a). Whereas Archer, using Campbell's (Reference Campbell1999) analysis, emphasizes that females gain less and lose more from overt fighting, he neglects to consider that females also may benefit far more than males from aggressively excluding one another.

Smuts (Reference Smuts, Smuts, Cheney, Seyfarth, Wrangham and Struhsaker1987a) argues that across primate species, males generally engage in sporadic but intense bouts of aggression for mates, whereas females engage in more chronic but low-grade aggression to attain resources. In humans, males compete for status and mates but they frequently retain these mates for long periods. The premium placed on virginal status and ensured paternity also means that once a male has successfully dominated his competitor to win a virginal female, losers will be less interested in the winner's wives. Further, male winners and losers may serve as future partners in cooperative group endeavors, including lethal coalitionary inter-group aggression. Human females, by contrast, continually compete to initiate and maintain long-term bonds with a mate who can provide prolonged aid. Eliminating competitors provides continuous benefits.

Archer's perspective that sex differences in aggression result from human males' confronting greater intrasexual competition for mates neglects the unique breeding challenges of each sex that human social structure likely evolved to satisfy.

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