The Evolving Father

How fatherhood differs across cultures and through time

Sex Differences in Fertility Preferences

Why men often want to have more kids than women

One Father's Attempt to Balance Fertility
In 2011, findings from a large study of Singles in America, sponsored by match.com, were publicized. This was a nationally representative probability sample of over 5000 singles aged 21-65. One of the findings that surprised many was that men were more oriented toward having kids than women.  Among men and women aged 21-35, a slight majority of men sought to have children, whereas 46% of women did. These were not dramatic differences, but did fly against any simplistic notion that women might have more babylust than men.

Far, far away, in Pimbwe villages in Tanzania, the anthropologist Monique Borgerhoff Mulder investigated fertility preferences among men and women. In a survey of fertility preferences—asking how many children women and men sought to have—among 177 Pimbwe in the mid-1990s, Borgerhoff Mulder found positive correlations between the desired fertility of husbands and wives. Additionally, men desired to have more children than women. The modal desired family size for men was 6 children, but the modal desired family size for women was 4 children.

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As it turns out, a sex difference in fertility preference has been documented in many places. Extending beyond singles in America or rural Tanzanians, it turns out in many other societies men have higher fertility preferences than women. As Sheldon Segal (2003) has noted, “Surveys have been done in Africa and Asia concerning husband’s attitudes toward fertility, contraceptive use, and reproductive preferences. Compared to their wives, men want more children, not fewer. In the west African countries in the survey, the ideal family size reported by men was nine, well above the upper limit preferred by women.” (p. 114).

Why might men have higher fertility preferences than women? Women bear the bulk of reproductive costs, beginning with nine months of gestation. The relative reproductive costs and benefits favor women cueing their fertility decisions to salient features of their socioecological context, which in practice means energetic factors (such as changes in food availability), health factors (illnesses), and social factors (such as availability of family support, including a prospective child’s father). Contrasted with a male perspective, the reproductive costs and benefits differ. That calculus, beginning with not having to gestate a baby for nine months, helps tilt men toward quicker and higher fertility figures. The bigger challenges for men are finding a partner willing to have children with him, and channeling his limited resources towards kids.

There are implications of sex differences in fertility preferences. Women tend to be more interested in and drivers of technologies (such as the Pill) constraining reproduction. When women have greater autonomy over reproduction, fertility decisions will likely be lower than when male reproductive decisions hold sway. Furthermore, while males sometimes employ techniques to constrain fertility (such as withdrawal or vasectomy), much of the male “sexual medicine” arsenal used in small-scale and larger contemporary societies is designed to enhance fertility; males are more likely to make use of plants or pills to treat their own impotence or to stimulate female sexuality than to suppress fertility, for example.

In a fertile world, men’s and women’s preferences may not completely align.

 

References:

Borgerhoff Mulder, M. (2009). Tradeoffs and sexual conflict over women’s fertility preferences in Mpimbwe. American Journal of Human Biology, 21, 478-487.

Gray, P. B., & Garcia, J. R. (2013). Evolution and human sexual behavior. Cambridge: Harvard University Press.

Segal, S. J. (2003). Under the Banyan tree. New York: Oxford University Press.

Peter B. Gray, Ph.D., is an associate professor of anthropology at the University of Nevada, Las Vegas. He is the coauthor of Fatherhood.

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