Same-sex attraction is associated with a direct reproductive cost, ie. a reduced number of biological children.
The current study aimed to assess this cost for different forms of sexual attraction (ie. only attracted to opposite sex, mostly attracted to opposite sex, equally attracted to both sexes, mostly attracted to same-sex, only attracted to same-sex), using 2 large nationally representative datasets (n = 15,208) from the USA. [For the purposes of our study, we employed data from the National Longitudinal Study of Adolescent to Adult Health (Add Health) 1994–14200816ya, which is a longitudinal study of a nationally representative sample of US adolescents in Grades 7 through 12 during the 1994–199529ya school year (Harris et al 200915ya).]
The results indicated that same-sex attraction was associated with substantial loss in direct reproductive output. More specifically, statistically-significant differences between the different types of same-sex attraction were found: Exclusive and mostly homosexual orientation identities were associated with the highest direct reproductive cost, while mostly attracted to opposite sex orientation and bisexuality identities were associated with lower direct reproductive costs. In addition, bisexual women did not differ statistically-significantly from exclusively heterosexual women in terms of their reproductive output.
The implications of these findings for the evolutionary origins of same-sex attraction are further discussed.
[Keywords: same-sex attraction, direct reproductive cost, homosexuality, bisexuality, lesbianism, sexual orientation]
