Recalled Childhood Separation Anxiety in Relation to Sex, Sexual Orientation, and Gender Identity in Thailand.

Same-sex sexual attraction is an evolutionary paradox. It is influenced by genes but also associated with reduced reproduction. An altruistic disposition toward kin could increase relatives' reproduction, thus addressing this paradox. Developmentally, such a disposition may manifest as anxiety during separation from kin. This hypothesis has been supported among androphilic (i.e. sexually attracted to males) males, but few similar studies of gynephilic (i.e. sexually attracted to females) females exist. We examined recalled childhood separation anxiety in Thailand and employed the largest and most sexually and gender-diverse sample to date ( = 1403). Among heterosexuals, men recalled less concern for parents' and siblings' well-being during separation than women. Androphilic males evidenced elevated concern for parents' and siblings' well-being during separation, and transfeminine androphilic males known as reported heightened anxiety when separated from parents. Among females, transmasculine gynephilic females known as recalled less concern about parents' well-being during separation than feminine females who are attracted to and known as . Bisexual women recalled less anxiety when separated from parents than and lesbian and heterosexual women. These findings suggest a disposition toward heightened kin-directed altruism is evident in childhood among androphilic males, but not gynephilic females.