Mate Guarding and Poaching

Like most birds and many other species, most people employ a socially monogamous mating strategy. At any given time, a person maintains a romantic relationship with only one other person in which both members of the relationship cooperate to maintain the relationship. This social relationship, however, does not guarantee sexual exclusivity. Although it may be socially undesirable, men and women sometimes engage in sexual behavior with people other than their partners. Keeping one's long-term mate from being sexually unfaithful is as much of a problem for people today as it was for our ancestors hundreds of thousands of years ago. Because this has been such a costly problem throughout human evolutionary [Page 1068]history, people today have evolved a series of cognitive and affective mechanisms that motivate behaviors intended to guard against such infidelities, as well as behaviors intended to circumvent the mate guarding behaviors of a potential mate's current partner. This entry discusses findings from recent research in the area of human romantic relationships suggesting how and why people keep their own mates from being sexually unfaithful and how and why other people evade those attempts.

Having one's mate be unfaithful can be costly for both men and women. Men whose partners are sexually unfaithful run the risk of being cuck-olded—unwittingly investing time, energy, and material resources in genetically unrelated offspring. In addition, a man whose partner has been unfaithful also risks permanently losing his partner to another man, effectively losing all previous investment in his partner and in the relationship, as well as all possibility of future reproduction with her. He must then expend effort finding another mate and developing a new relationship. Women, on the other hand, are never at risk for cuckoldry. When a woman has a child, she knows that the child is hers. However, women still are subject to negative consequences of their partner's infidelity. A woman whose partner defects the relationship, even temporarily, risks losing her partner's investment in herself and her offspring. If she is interested in establishing a new romantic relationship, she must expend effort finding another mate who is willing to invest in her and any children she may have. Given the reproductively costly consequences of a partner's infidelity, then, people in romantic relationships perform a variety of behaviors intended to discourage their mates from defecting from the relationship in the form of an infidelity.