Himba: Despite aspirational preferences, couples who are more closely matched in term of mate value reported greater relationship quality, measured through frequency of interactions, reported sexual histories, and partnership length

The effect of mating market dynamics on partner preference and relationship quality among Himba pastoralists. Sean Prall, Brooke Scelza. Science Advances, May 4 2022, Vol 8, Issue 18 • DOI: 10.1126/sciadv.abm5629

Abstract: Relative mate value has long been believed to be a critical component of mate choice in humans. However, most empirical work focuses on preferences rather than actual pair formation, and data connecting partner preferences, partnership formation, and relationship quality remain rare. Here, we estimate mate value using >12,000 ratings by opposite-sex, in-group members to understand both hypothetical partnership preferences and actualized relationship dynamics. When evaluating hypothetical partnerships, people generally prefer individuals whose mate value is higher than their own, indicating an aspirational matching strategy. However, mate value comparisons of individuals in marital and nonmarital relationships show a positive correlation, suggesting that individuals tend to pair up with similarly desirable individuals. Furthermore, despite aspirational preferences, couples who are more closely matched reported greater relationship quality, measured through frequency of interactions, reported sexual histories, and partnership length.

DISCUSSION

Real-world partner dynamics are notoriously difficult to study, as they require longitudinal data and an ability to evaluate the pool of prospective suitors people are drawing partners from. Here, by combining a novel rating system with ethnographic interviews in a largely endogamous population of Himba pastoralists, we can determine people’s position within the local mating market and use that to evaluate both their preferences and their realized partnerships. Using preference data, we test two competing hypotheses of partner preference to examine whether participants prefer more desirable partners or adhere to mating market predictions and prefer partners of similar desirability to themselves. Our data show that participants’ preferences corresponded most closely with an aspirational mate choice strategy, with individuals generally preferring partners who were more desirable than themselves. While these relationship preference ratings represent idealized preferences and not actual attempts at relationship formation, they correspond well with research from online dating markets (18), indicating that aspirational mate choice may not just be a feature of online dating markets or experimental paradigms but a more common feature of people’s preferences.

However, while Himba preference data conform most closely to an aspirational model, their relationship histories correspond best with the biological mating market approach. In both marital and nonmarital relationships, partners tend to be similar in relative mate value, exhibiting a moderate correlation. When examining reported sexual history data, similar dynamics are also found. Dyads of similar mate value are more likely to have reported a previous sexual relationship. In other words, while more desirable individuals are generally preferred by all, in the context of relationship formation, Himba men and women tend to pair up with similarly desirable partners. This may be a function of the most desirable members of the mating market exerting greatest choice in their partners, resulting in assortative mating.

Results from our relationship surveys help to explain the seemingly contradictory evidence for aspirational preferences and largely assortative partnerships. Well-matched dyads have longer-lasting relationships and report being in more frequent phone contact. In addition, participants who had partners of higher mate value were more likely to report that those partners had many additional partners. These findings suggest that mate value disparities result in relatively unstable relationships where the more desirable partner may be more likely to pursue other options on the mating market. This mirrors previous work showing that mate value disparities can result in lower relationship satisfaction (20). So while mismatched partnerships occur, they are less likely to be durable and long lasting, which could be contributing to the positive correlation in mate value between partners in extant dyads.

These results also highlight sex-specific adjustments in preference in response to local conditions. Sex ratio estimates in this population are remarkably female skewed (32). On the basis of mating market predictions, a female-biased sex ratio should result in high bargaining power for men, allowing them to be choosier in partner selection. This prediction is borne out in our model results, which indicate a stark sex difference in rater desirability on preference. Men, but not women, who have higher mate value are more discerning. However, this result should be considered alongside the other trend in our data, which shows that women in general are choosier than men. Women are much more likely than men to give potential partners the lowest possible desirability rating (Fig. 2). It may be that a female-biased sex ratio makes women less susceptible to intrapopulation market effects, where they are less likely to exert selective preferences due to market position, while still exhibiting more generalized partner discrimination. Conversely, men who are generally less choosy cross-culturally exhibit higher market value when scarce. These results highlight the importance of interactions between generalized sex-specific preferences and intrapopulation market effects.

As R. W. Emerson stated, “we aim above the mark to hit the mark.” Our data reflect just this type of strategy. When looking at preferences alone, Himba are shown to aspire toward partnerships with those of greater mate value than their own. These preferences indicate that Himba are well attuned to mating market dynamics and their place within them. However, the operationalization of those dynamics means that actual partnerships shake out into a mostly assortative pattern and further that assortative matches tend to be more stable. The combination of a biological market approach with the aspirational mate choice strategy fits well for Himba and may be more generally indicative of partnership dynamics in real-world contexts.