Kin-directed altruism and the evolution of male androphilia among Istmo Zapotec Muxes

Abstract

Male androphilia (i.e., sexual attraction and arousal to adult males) is considered an evolutionary puzzle because it reduces direct reproduction, but is influenced by genetic factors, reliably occurs across cultures, and has persisted over evolutionary time. The kin selection hypothesis states that genes for male androphilia can be maintained in a population if the costs of not reproducing directly are offset by enhancing the reproduction of kin. We tested this hypothesis among the Istmo Zapotec of Oaxaca, Mexico, where transgender and cisgender androphilic males are known as muxe gunaa and muxe nguiiu , respectively. We compared altruistic tendencies towards kin and non-kin children between muxe nguiiu ( n = 106), muxe gunaa ( n = 106), gynephilic men (i.e., men sexually attracted and aroused to adult females; n = 172), and androphilic women ( n = 130). We also assessed whether the sisters of muxes ( n = 96) reported receiving more childcare support from their muxe sibling compared to women with only gynephilic brothers ( n = 65). The results showed that cisgender and transgender muxes reported more kin-directed altruistic tendencies than men. Muxe nguiiu also reported more kin-directed altruistic tendencies than women. When controlling for altruistic tendencies towards non-kin children, both muxe types exhibited more kin-directed altruistic tendencies than men and women. Women with muxe siblings reported receiving more childcare support from these relatives compared to women with only gynephilic brothers. These findings provide support for the kin selection hypothesis and highlight its potential role in elucidating the evolutionary paradox of male androphilia.