Putting empathy and emotion aside for a moment, evolutionary analysis may explain moralizing about infidelity. The essential question is, when is it reproductively advantageous for one party to restrict the sexual behavior of another? For females with high-quality mates, monogamy is clearly advantageous, as the male’s resources are exclusively devoted to the female’s offspring. Low-quality males also benefit from monogamy as, under polygamy, they are not regularly reproducing. From the perspective of any male, the less other males copulate, the better. For high-quality males, provided there remains some opportunity for unpunished, extra-pair copulation, the general proscription of polygamy is not especially costly. Low-quality females, however, lose something. They no longer have an option between sharing in the resources of a high-quality male and having the full resources of a lower-quality male. On the whole, a reasonable case can be made for a selective pressure promoting a species-typical behavior that enforces monogamy within one’s community, a moralization of infidelity.
- Gelada Baboons Keep Sexual Infidelity Hush-Hush (livescience.com)
- Are humans monogamous? (theratchet.ca)