Alternative views on the role of sex steroid hormones on the emergence of phenotypic diversity in female sexual orientation

In their Target Article, Luoto, Krams, and Rantala (2018) used the four questions of Tinbergen to gain a better understanding of the evolution and developmental origin of female sexual orientation and the variety of homosexual phenotypes reported in women. In their endeavor, Luoto et al. propose a compelling model to explain the origin of female homosexuality, or what they carefully call female non-heterosexuality to take into account the greater flexibility that women exhibit regarding the sex of their sexual partner. Most studies on the origin of sexual orientation consider it as a binary variable with exclusive heterosexuals and homosexuals placed at the two extremes of a continuum. This might be true for male sexual orientation which is characterized by a bimodal distribution with the highest frequencies at the two extremes. By contrast, female sexual orientation shows a more spread out distribution of frequencies of intermediate phenotypes and a higher prevalence of bisexuality...