Introduction

Male sexual jealousy is a frequently cited cause of non-lethal and lethal violence in romantic relationships (e.g. Buss, 2000; Daly & Wilson, 1988; Daly, Wilson, & Weghorst; 1982; Dutton, 1998). Evolutionary psychologists hypothesized two decades ago that male sexual jealousy may have evolved to solve the adaptive problem of paternity uncertainty (Daly et al., 1982; Symons, 1979). Unlike women, men face uncertainty about the paternity of their children because fertilization occurs within women. Without direct cues to paternity, men risk cuckoldry, and therefore might unwittingly invest in genetically unrelated offspring. Cuckoldry is a reproductive cost inflicted on a man by a woman's sexual infidelity or temporary defection from her regular long-term relationship. Ancestral men also would have incurred reproductive costs by a long-term partner's permanent defection from the relationship. These costs include loss of the time, effort, and resources the man has spent attracting his partner, the potential misdirection of his resources to a rival's offspring, and the loss of his mate's investment in offspring he may have had with her in the future (Buss, 2000).

Expressions of male sexual jealousy historically may have been functional in deterring rivals from mate poaching (Schmitt & Buss, 2001) and deterring a mate from a sexual infidelity or outright departure from the relationship (Buss et al., 1992; Daly et al., 1982; Symons, 1979). Buss (1988) categorized the behavioral output of jealousy into different “mate-retention” tactics, ranging from vigilance over a partner's whereabouts to violence against rivals (see also Buss & Shackelford, 1997).