The target article (Wahring et al., abstract) proposes that, contrary to some prevailing beliefs, “relative to women: (a) men expect to obtain greater benefits from relationship formation and thus strive more strongly for a romantic partner, (b) men benefit more from romantic relationship involvement in terms of their mental and physical health, (c) men are less likely to initiate breakups, and (d) men suffer more from relationship dissolution.” This commentary has no issues with these propositions, nor with its “theoretical explanations based on differences between men and women in the availability of social networks that provide intimacy and emotional support.” Rather, it emphasizes the point that these explanations are “proximate” rather than “ultimate” explanations à la Mayr (Reference Mayr1961). That they are proximate does not mean that it is not useful to discuss them in detail. However, the combination with the ultimate explanations will likely provide a deeper understanding of the relevant factors (see, e.g., Lira et al., Reference Lira, Holder and Gardner2024; Majorova, Reference Majorova2022; Zietsch et al., Reference Zietsch, Sidari, Murphy, Sherlock and Lee2021).

The ultimate explanation this note emphasizes is the very big gender difference in cost/benefit ratios between men and women in reproductive fitness-enhancing effects of having sexual partners. This big gender difference is due to the fact that, while a man only needs a short time to pass on his genes through sexual interaction, a woman needs 9 months of gestation plus some years of nursing and caring to ensure the survival of the child. A surviving child carries 50% of genetic information each from its mother and father, but the father typically spends much less time and effort than the mother. Hence, there is big gender difference in the cost/benefit ratio. This big gender difference makes men and women, through natural selection, have big differences in their preferences and behaviors. These, in turn, have relevance to the major propositions of this target article. For example, this big gender difference directly makes “men benefit more from romantic relationship involvement,” hence “men are less likely to initiate breakups,” and “suffer more from relationship dissolution.” In addition, it also helps to promote the evolution of factors, such as having a stronger sex drive, that make men “strive more strongly for a romantic partner,” avoid breakups, etc., that enhance their fitness. Thus, the present commentary suggests that more emphasis should be placed on this ultimate explanation. However, a full examination is beyond the scope of this short commentary.

The target article does mention “parental investment and sexual strategies theory” (Wahring et al., sect. 2.1, para. 2; see also sect. 2.4), which is related to the big gender difference mentioned above. However, the target article treats this as a “perspective” explaining the propositions, but not at the level of an “ultimate” explanation à la Mayr (Reference Mayr1961).

In addition to the emphasis on this ultimate explanation in terms of the big gender difference, this note also wishes to draw attention to several points below.

First, the target article proposes that the four important differences (a) to (d) (as outlined at the beginning of this commentary), “are primarily rooted in the broader notion that men, compared to women, depend more strongly on their romantic partners for emotional support and intimacy needs” (Wahring et al., sect. 6, para. 1). While this may be true for other forms of intimacy needs, for the intimacy need of sexual intercourse, the reverse may be true as female prostitutes are generally more available to satisfy men’s needs here than male prostitutes for women’s needs. The higher availability of female prostitutes is at least partly due to the higher sex drive of men in comparison to women.

Second, while the point that “Single men, for example, typically strive harder to initiate romantic relationships than single women do” (Wahring et al., sect. 1, para. 2) may be due to factors as explained in the target article and the ultimate explanation of this commentary, it could also be due to the social conditioning requiring men to be more active and women more passive, especially in countries with Eastern cultures. (See, e.g., Björkqvist, Reference Björkqvist2018; Cheong, Reference Cheong2020; Hyde, Reference Hyde1984; Qunying, Reference Qunying2007; Singh, Reference Singh2024).

Third, does the fact that women have menopause around the age of their mid-40s, after which they are no longer reproductively active, while men can reproduce (with the help of women, of course) until a very old age, make important differences? This gender difference is due to the fact that babies need their mother to nurse and care for them for many years. Even if women have babies after their mid-40s, they may not have sufficiently long living years to care for them until reproductive ages. This was especially so during our long history of evolution, when life expectancy was much shorter than it is currently. On the other hand, while fathers’ contributions are also useful to the survival of the children, they are not as essential as those of mothers. Thus, Darwinian evolution results in early menopause for women to allow them to concentrate on caring for their young children born earlier, instead of wasting resources on having more babies who are unlikely to survive long. Again, further studies are needed.