Running head: HUMAN FEMALE SEXUAL ORIENTATION 1 [in press, Evolutionary Psychological Science, July 2018] The Evolution of Human Female Sexual Orientation Austin John Jeffery, Todd K. Shackelford, Virgil Zeigler-Hill, Jennifer Vonk, and Melissa McDonald Oakland University Address correspondence to Austin John Jeffery, Oakland University, Department of Psychology, Rochester, Michigan 49309. Email:
[email protected]. HUMAN FEMALE SEXUAL ORIENTATION 2 Abstract Female sexual orientation has received less theoretical and empirical attention than male sexual orientation and few reviews are devoted to female sexual orientation. Moreover, research investigating female sexual orientation often underappreciates insights afforded by evolutionary theory. This review begins with an overview of the literature on female sexual identification, sexual perception, sexual fluidity, sexual expression, and the biology of female sexual orientation. Female same-sex sexual behaviors in the non-human apes are then described, providing a comparative context for the following discussion of hypotheses for the evolution of human female same-sex sexual attractions and behaviors. These hypotheses are organized as byproduct hypotheses or adaptation hypotheses and we include discussions of dysfunction, heterosis, sexual antagonism, epigenetics, weak selection, self-domestication, sexual frustration, mate attraction, alloparenting, polygyny, and other topics. We conclude by highlighting the challenges posed by evolutionary studies of human psychology. Keywords: evolution, female homosexuality, female sexuality, sexual orientation HUMAN FEMALE SEXUAL ORIENTATION 3 The Evolution of Human Female Sexual Orientation Same-sex sexual attractions and behaviors, to the extent that they are exclusive and attributable to genetic influence, are often presented as deleterious because they may subtract from lifetime reproductive success (Gates, 2013). Yet, same-sex sexual attractions and behaviors are expressed by a large minority of humans.