Societal norms against fornication, understood as prohibitions on sexual relations outside of marriage, tend to redistribute opportunities for sexual and reproductive success among men in ways that are more egalitarian than in settings without such restrictions. In societies where premarital or extramarital sex is common and relatively unconstrained, male sexual and reproductive success often becomes strongly stratified. A small proportion of men, usually those with higher social status, wealth, physical attractiveness, or charisma, can secure disproportionate access to sexual partners. These men are able to accumulate reproductive advantages, sometimes fathering many children, while a significant proportion of men remain excluded or experience very limited reproductive success. This creates a highly unequal landscape where male competition is extreme, and reproductive opportunities are concentrated among a few.

Norms against fornication seek to level this disparity by channeling sexual access into the institution of marriage. Marriage, especially when culturally linked to monogamy, restricts the ability of higher-status men to monopolize multiple partners simultaneously. By binding sexual relations to a socially sanctioned contract, most men, regardless of their attractiveness or status, have a reasonable chance of finding a partner and establishing a family. The institution effectively places guardrails on sexual competition by requiring that relationships conform to a publicly recognized framework, where pairings are stabilized and opportunities for sexual access are spread more evenly across the male population. This reduces the reproductive skew that would otherwise favor a small elite.

The norm also reduces the reproductive vulnerability of lower-status men. Without restrictions, these men might be systematically excluded from mating opportunities, leading to high rates of bachelorhood and childlessness. By limiting female sexual choice primarily to the context of marriage, society dampens the competitive advantage of the most attractive or resource-rich men and ensures that sexual access is mediated by family, community, or economic arrangements rather than unbounded individual preference. This does not erase inequality altogether, but it compresses the range of outcomes, preventing extreme reproductive success at the top and extreme exclusion at the bottom.

In this way, societal prohibitions on fornication serve as a form of reproductive egalitarianism among males. They constrain the natural tendencies of sexual selection to concentrate opportunities in the hands of a minority, and instead create conditions where a much broader portion of men can expect to achieve both sexual and reproductive success. The effect is to shift male competition from raw sexual access toward qualities like stability, provision, and social recognition, which can be more evenly distributed across the population than sheer attractiveness or dominance. Over time, this stabilizes communities by reducing resentment, violence, and the destabilizing tendencies.