In an anthropological classic, The Sexual Life of Savages, Bronislaw Malinowski commented on the connections between sexuality and fatherhood among Trobriand Islanders living off the coast of New Guinea. In explaining why fathers might give gifts to their own children, rather than nieces and nephews, he wrote, “The natives explain this anomalous state of things by the father’s partiality to his children, which, in its turn, is accounted for by his relation to their mother. The natives say that his free gifts to the children are a reward for the free cohabitation which he enjoys with his wife.” (p. 178)
There’s something deep here, a connection between sexual access and paternal care. From first principles of sexual selection, male reproductive success tends to be ultimately limited by access to reproductive females. Sexual selection is thought to have shaped male anatomy, physiology, and behavior to seek to compete successfully with other males and court females. Sexual selection appears to have favored evolution of capacities and motivations that make males strive for sexual access. Since females, by first principles of sexual selection, tend to be the limiting sex, they can offer sexual access for benefits they seek, including paternal care. Males may thus provide paternal care as a perk for females providing sexual access. Males provide parental care, in evolutionary biological terms, as a form of mating effort.
None of that sounds very romantic. But there are clues that this sort of dynamic helps make sense of some of the broad patterns of paternal care, in other primates, but also among humans like Malinowski found in the Trobriands. In seminal work with baboons, Barbara Smuts noted that males formed ‘friendships’ with particular females, in part by being nice to her offspring. Those kindnesses were, in some cases, paid back downstream with sexual access to her. In humans, one interpretation for why stepfathers may provide considerable time and resources to another man’s children is that stepfathers do so as a form of mating effort provided to the child’s mother; his care is part of what provides sexual access to her. Among men in the 1990s Albuquerque male project, for example, coresidential fathers provided the most time and money to their kids, but coresidential stepfathers provided lots of both too, with one interpretation that doing so was part of maintaining sexual access to the stepchild’s mother.
Is all male care mating effort? While some extreme positions would argue yes, the data indicate males provide care for other reasons than garnering current sexual favors. In a variety of studies, from the U.S. to South Africa, biological fathers commonly provide more care than stepfathers to children; that shouldn’t be the case if males only provided care for sexual access. When men are stripped of sexual access to a child’s mother—through oversees work, while being imprisoned, when social sanctions intervene (e.g., European elites fathering ‘bastard’ children) to use extremes—we can identify plenty of still-caring fathers. Less dramatically, many divorced or separated fathers, who no longer have sexual relationships with their child's mother, continue to devote time and resources to their kids. Additionally, within partnerships, in late pregnancy, early postpartum, and with advancing age when frequencies of sex may diminish, males may continue to provide care. In such cases, the importance of ongoing sexual access may be outweighed by other factors, from the strength of an emotional tie to a child’s mother, to other kin’s influence, to a man’s direct desire to care for his children (regardless of sexual purse strings).
Gray, P. B. , & Anderson, K. G. (2010). Fatherhood: Evolution and human paternal behavior. Cambridge, MA: Harvard University Press.
Gray, P. B. , & Garcia, J. R. (2013). Evolution and human sexual behavior. Cambridge, MA: Harvard University Press.
Malinowski, B. (1938). The sexual life of savages. Boston: Beacon Press.
Muller, M. N., & Emery Thompson, M. (2012). Mating, parenting, and male reproductive strategies. In. J. C. Mitani, J. Call, P. M. Kappeler, R. A. Palombi, & J. B. Silk (Eds.), The evolution of primate societies (pp. 387-411). Chicago: The University of Chicago Press.
Smuts, B. B., & Gubernick, D. J. (1992). Male-infant relationships in nonhuman primates: Paternal investment or mating effort? In B. S. Hewlett (Ed.), Father-child relations: Cultural and biosocial contexts, (pp. 1-30). New York: Aldine.