Encyclopedia of Evolutionary Psychological Science

Living Edition
| Editors: Todd K. Shackelford, Viviana A. Weekes-Shackelford

Sex Differences

  • Michelle Escasa-DorneEmail author
  • Carol Franco
  • Peter Gray
Living reference work entry
DOI: https://doi.org/10.1007/978-3-319-16999-6_17-1


Single Mother Parental Investment Mate Preference Single Father Human Mate Preference 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



Evolutionary theory predicts sex differences among humans, which may extend (or be amplified) after having children.


This entry provides an evolutionary theoretical framework to help explain sex differences in mate preferences among human parents. Few data enable directly testing sex differences in mate preferences. However, various lines of inferential evidence, including patterns of sexual behavior, causes for divorce, and dating information on single parents, are presented.

Sex Differences After Having Children

The evolutionary foundation of sex differences in mate preferences draws upon theoretical insight into the evolution of sex differences in reproductive effort more broadly (see Sex Differences in Human Mate Preferences; Sex Differences in Parenting and Parental Investment). Sex differences have been variably linked to gamete size (see Sex Difference in Gamete Production; Gamete Size), relative parental investment, potential reproductive rate, and actual reproductive rate. If females typically have a lower actual reproductive rate than males, this observation helps account for sex differences in mate preferences; for example, males may have lower minimal standards in a mate given relative reproductive constraints.

Sex differences in mate preferences that preexist having children may persist after having children. However, there is reason to theorize that having children may also alter the nature of sex differences in mate preferences. Reproductive effort can be portioned into mating and parenting effort. Multiple lines of evidence from various societies indicate that women allocate a relatively higher proportion of their reproductive effort to parenting effort compared to men. After having young children, women may expend considerable time and energy nursing their offspring and tend to engage in higher rates of direct child care than fathers. For such reasons, sex differences in actual reproductive rates may be magnified, contributing in turn to life history stage-specific sex differences in mate preferences. For example, mothers may place a greater premium on a partner’s ability to provide the resources she and her child need than she did before having children, compared with fathers’ preferences (see Weeks-Shackelford et al. 2007).

There are few data directly addressing sex differences in human mate preferences after having children. In a recent study of 747 single parents drawn from a demographically representative US sample of adult singles, several sex differences in mate preferences emerged among parents (Gray et al. 2016). Mothers were more apt than fathers to take seriously their children’s opinion of their dating partner, while fathers were more likely than mothers to allow their children to set them up on dates. In a related national US sample, single fathers reported more often thinking about sex, having sex, having more sexual partners the past 12 months actively seeking a new partner, and going on more dates compared with single mothers (Gray et al. 2015a). The remainder of this entry draws largely upon inferential studies to help shed light on sex differences in mate preferences among parents.

Classic research on sex differences in mate preferences showed that women tended to value cues of male status and resources more than did men, whereas men tended to value cues of a partner’s attractiveness more than did women. There is good reason to believe these sex differences persist, if not increase in magnitude, after having children. Sources of marital conflict and divorce highlight sex differences in the causes of relationship challenges. These show in Western and cross-cultural records that men are more likely than women to specify infertility and infidelity as causes of divorce; these observations fit with a view that men’s mate preferences are attuned to cues of fertility and fidelity. Conversely, women’s grounds for divorce more often cite physical abuse and inadequate resource provisioning, consistent with mate preferences that value relative safety and support in helping raise her offspring.

Research suggests sex differences in sexual desire and partner variety after having children (Gray and Garcia 2013). These observations are related to mate preferences – in whether desiring to mate at all and with how many partners. Importantly, these aspects of sexuality are likely magnified in later pregnancy and in early stages after having children relative to pre-parental or later-parental stages. A way to conceptualize these enhanced sex differences begins with the recognition that women’s reproductive effort privileges current over future reproduction during pregnancy and intensive postpartum parental care (Escasa-Dorne et al. 2013). Time and energy devoted to caring for a newborn draws away from maintaining psychological and physiological support for conceiving the next child. These life history shifts are orchestrated in part by changes in maternal hormone levels. Mothers’ testosterone and estradiol levels decrease after birth, two hormones important in sexual activity. Conversely, elevated oxytocin and prolactin levels, which increase in women after birth to aid in lactation and direct maternal care, may have consequences for partnership behaviors (i.e., enhancing an infant bond at expense to that with a mate).

While becoming a father can impact men’s psychology, physiology, and overall reproductive effort, those relative impacts are less than among mothers. Consistent with such views, mothers of young children tend to exhibit lower sexual desire and more pain during sex compared to fathers of young children. In several societies such as St. Louis in the mid-twentieth century and among the Ngandu farmers of Central Africa, the increased sexual conflict over desire for sex has been reported to lead to elevated risk of fathers seeking extra-pair partners. In a study of some 3410 Jamaican fathers of newborns, about half of men reported no sex the previous week. Yet approximately 30 % of fathers reported multiple sexual partners the previous 12 months, with younger men, men in visiting relationships, and men in lower quality relationships those more likely to report more sexual partners (Gray et al. 2015b). Relatedly, some mothers of infants in Manila, the Philippines, reported engaging in sex with their husband in what amounts to a relationship maintenance strategy – having sex to appease a valued partner rather than driven by one’s own inner desire (Escasa-Dorne 2015).

Most of human reproduction ancestrally and today occurs within long-term partnerships that are often codified by marriage (Gray and Garcia 2013). The same classic studies of cross-cultural mate preferences that showed some evidence of sex differences also showed considerable sex similarity: the most preferred traits indicated the importance of character and compatibility, consistent with a preference for cues suggesting success in maintaining a long-term partnership. Continued maintenance of a long-term partnership may be beneficial after having children, given the considerable time and resources humans expend on their offspring. Nonetheless, the death of a partner or dissolution of a relationship regularly leaves many parents single. Hunter-gatherer demographic studies suggest that divorces and re-partnering after having had children are regular occurrences. Yet apart from the US study cited above, what sex differences might be expected in the mate preferences of single parents?

Inferential insight suggests single mothers may be more attuned to partner cues indicative of safety for herself and her offspring. Research by Martin Daly and Margo Wilson, among others, showed that young children face elevated risk of physical abuse and death among step-figures, particularly stepfathers. A public health campaign deployed in parts of the USA entitled, “Choose Your Partner Carefully” focuses on single mothers rather than single fathers for this reason. Mothers may prefer cues of a potential partner’s kindness (e.g., in faces, voices, and personality), perhaps to invest in her and her offspring but also to do her and her offspring less harm (Escasa-Dorne et al. 2013; Weeks-Shackelford et al. 2007). Relatedly, among Hadza hunter-gatherers of Tanzania, breastfeeding women preferred high-pitched male voices while women who were not breastfeeding preferred low-pitched voices (Apicella and Feinberg 2009). Several studies from the UK, the USA, and the Philippines focused on mothers’ evaluations of male faces have shown that mothers of young children exhibited preferences for feminine male faces (Cobey et al. 2014; Escasa-Dorne et al. 2016). Moreover, parenting effort may influence women’s preferences for a healthy partner, particularly in high pathogen load areas. For example, pregnant and breastfeeding Hadza women had an increased preference for symmetrical male faces compared to non-pregnant and non-nursing women (Little et al. 2007).

All else being equal, single parents may hold lower mate value on the mating market. A parent’s child can take away time spent between partners, and children may require resources and time that a prospective partner may not wish to share. In the same US singles study previously noted, there was no sex difference in the interest of single parents in dating other single parents (Gray et al. 2016). Yet single parents may collectively express less discerning mate preferences, consistent with a lower mate value attendant to having children. Relatedly, it may benefit a single parent to prefer a partnership with someone who has a lower self-perceived mate value or lower mate quality, as it may free them from having to continuously maintain the relationship (i.e., mate guarding) allowing a parent to direct her attention to parenting. It also bears underscoring that many single parents weigh their children’s presence and views in parental dating and mating behavior.

Individual mate preferences are contingent on individual (e.g., mate value), relationship (e.g., relative mate values between partners), and wider social contextual (e.g., availability of alternative partners) factors. This means that the nature of sex differences in parents’ mate preferences is also contingent on these same considerations. Just as variation in the social ecology of physical threats may impact how desirable a man’s formidability or other cues indicative of protective capacity, so the magnitude of parents’ sex differences in mate preferences for cues of protective abilities may also vary. Future work might seek to quantify the relevance of variable male provisioning, other features of a sexual division of labor, parental manipulation, and single parent child custodial time, among other factors, in impacting sex differences in parents’ mate preferences.


Few studies directly address sex differences in mate preferences after having children. However, multiple inferential lines of evidence such as patterns in sexual behavior, causes of divorce, and cross-cultural data on mothers’ mate preferences point to the continuation if not amplification of sex differences in mate preferences after having children.



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Copyright information

© Springer International Publishing Switzerland 2016

Authors and Affiliations

  • Michelle Escasa-Dorne
    • 1
    Email author
  • Carol Franco
    • 2
  • Peter Gray
    • 2
  1. 1.Department of AnthropologyUniversity of Colorado-Colorado SpringsColorado SpringsUSA
  2. 2.Department of AnthropologyUniversity of Nevada-Las VegasLas VegasUSA