Why is Sex Fun?: the evolution of human sexuality by Jared Mason Diamond Page B

more than a dozen children over the course of their lives. The record lifetime number of offspring for a woman is a mere sixty-nine (a nineteenth-century Moscow woman who specialized in triplets), which sounds stupendous until compared with the numbers achieved by some men to be mentioned below.
    Hence multiple husbands do not help a woman to produce more babies, and very few human societies regularly practice polyandry. In the only such society that has received much study, the Tre-ba of Tibet, women with two husbands have on the average no more children than women with one husband. The reasons for Tre-ba polyandry are instead related to the Tre-ba system of land tenure: Tre-ba brothers often marry the same woman in order to avoid subdividing a small landholding.
    Thus, a woman who “chooses” to care for her offspring is not thereby foreclosing other spectacular reproductive opportunities. In contrast, a polyandrous female phalarope produces on the average only 1.3 fledged chicks with one mate, but 2.2 chicks if she can corner two mates, and 3.7 chicks if she can corner three. A woman also differs in that respect from a man, whose theoretical ability to impregnate all the women of the world we have already discussed. Unlike the genetic unprofitability of polyandry for Tre-ba women, polygyny paid off well for nineteenth-century Mormon men, whose average lifetime output of children increased from a mere seven children for Mormon men with one wife to sixteen or twenty children for men with two or three wives, respectively, and to twenty-five children for Mormon church leaders, who averaged five wives.
    Even these benefits of polygyny are modest compared to the hundreds of children sired by modern princes able to commandeer the resources of a centralized society for rearing their offspring without directly providing child care themselves. A nineteenth-century visitor to the court of the Nizam of Hyderabad, an Indian prince with an especially large harem, happened to be present during an eight-day period when four of the Nizam's wives gave birth, with nine more births anticipated for the following week. The record for lifetime number of offspring sired is credited to Morocco's Emperor Ismail the Bloodthirsty, father of seven hundred sons and an uncounted but presumably comparable number of daughters. These numbers make it clear that a man who fertilizes one woman and then devotes himself to child care may by that choice foreclose enormous alternative opportunities.
    The remaining factor tending to make child care genetically less rewarding for men than for women is the justified paranoia about paternity that men share with the males of all other internally fertilized species. A man who opts for child care runs the risk that, unbeknownst to him, his efforts are transmitting the genes of a rival. This biological fact is the underlying cause for a host of repulsive practices by which men of various societies have sought to increase their confidence in paternity by restricting their wife's opportunity for sex with other men. Among such practices are high bride prices only for brides delivered as proven virgin goods; traditional adultery laws that define adultery by the marital status only of the participating woman (that of the participating man being irrelevant); chaperoning or virtual imprisonment of women; female “circumcision” (clitoridectomy) to reduce a woman's interest in initiating sex, whether marital or extramarital; and infibulation (suturing a woman's labia majora nearly shut so as to make intercourse impossible while the husband is away).
    All three factors-sex differences in obligate parental investment, alternative opportunities foreclosed by child care, and confidence in parenthood-contribute to making men much more prone than women to desert a spouse and child. However, a man is not like a male hummingbird, male tiger, or the male of many other animal species, who can safely fly or walk away immediately after