The Evolution of Human Homosexual Behavior

Abstract

Homosexuality presents a paradox for evolutionists who explore the adaptedness of human behavior. If adaptedness is measured by reproductive success and if homosexual behavior is nonreproductive, how has it come about? Three adaptationist hypotheses are reviewed here and compared with the anthropological literature. There is little evidence that lineages gain reproductive advantage through offspring care provided by homosexual members. Therefore, there is little support for the hypothesis that homosexuality evolved by kin selection. Parents at times control children's reproductive decisions and at times encourage children in homosexual behavior. There is therefore more support for the hypothesis of parental manipulation. Support is strongest, however, for the hypothesis that homosexual behavior comes from individual selection for reciprocal altruism. Same-sex alliances have reproductive advantages, and sexual behavior at times maintains these alliances. Nonhuman primates, including the apes, use homosexual behavior in same-sex alliances, and such alliances appear to have been key in the expanded distribution of human ancestors during the Pleistocene. Homosexual emotion and behavior are, in part, emergent qualities of the human propensity for same-sex affiliation. Adaptationist explanations do not fully explain sexual behavior in humans, however; social and historical factors also play strong roles.

Testing the Affiliation Hypothesis of Homoerotic Motivation in Humans: The Effects of Progesterone and Priming

“…Sexual orientation is commonly understood as patterned sexual desire that may lead to sexual behavior with members of one or the other sex. However, consonant with the functional explanations to be discussed below, much, if not most, same-sex sexual behavior occurs in those who do not identify as exclusively homosexual in orientation (Diamond & Wallen, 2011;Kinsey, Pomeroy, & Martin, 1948;Kirkpatrick, 2000). Our theoretical focus here is on a broad category of behavior, that which is erotic and occurs with members of the same sex, and its hormonal and motivational underpinnings (which include, but are not limited to, sexual desire); we consider sexual orientation or identity only secondarily, as this is not isomorphic with behavior.…”

“…Many individuals appear capable of sexual arousal toward members of the same sex under the right circumstances (e.g., during adolescence; in initiation rites, see Muscarella, 2006), and the ethnographic record indicates that same-sex sexual behavior is found in a majority of societies, spanning a wide range of social complexity, and at times occurring at fairly high frequencies (Kirkpatrick, 2000;Muscarella, 2007;Ross & Wells, 2000; see also Rind & Yuill, 2012). In laboratory studies, self-identified heterosexual women, on average, have been shown to have a generalized genital response to both sexes, while heterosexual men have been shown to have a modest genital response to male sexual stimuli (e.g., Chivers, Rieger, Latty, & Bailey, 2004;Chivers, Seto, Lalumiere, Laan, & Grimbos, 2010;Rieger, Chivers, & Bailey, 2005).…”

“…In laboratory studies, self-identified heterosexual women, on average, have been shown to have a generalized genital response to both sexes, while heterosexual men have been shown to have a modest genital response to male sexual stimuli (e.g., Chivers, Rieger, Latty, & Bailey, 2004;Chivers, Seto, Lalumiere, Laan, & Grimbos, 2010;Rieger, Chivers, & Bailey, 2005). This has led a number of investigators to propose that same-sex sexual behavior may have some direct adaptive value (Kirkpatrick, 2000;Muscarella, Cevallos, Siler-Knogl, & Peterson, 2005).…”

“…Same-sex sexual contact has been found in 67% of cultures in the Human Relations Area Files (Kirkpatrick, 2000), and the practice of such behavior by individuals who also engage in opposite-sex sexual contact has been prominent in many culture regions for centuries (Ross & Wells, 2000). Working in parallel, drawing on cross-species comparisons and extensive ethnographic and historical materials, Kirkpatrick (2000) and Muscarella (2000) presented overlapping evolutionary models arguing that human same-sex sexual behavior serves the adaptive function of promoting alliance formation and maintenance (Muscarella et al 2005; see also Rind & Yuill, 2012).…”

Die drange van hulle hart... (Rom 1:24–27)

“…Wat vir ons seker is, is dat homoseksualiteit deel van seksuele diversiteit is. Daar is interessante (en selfs oortuigende) evolusionistiese uiteensettings van hoe homoseksuele gedrag deel geword het van die menslike spesie se oorlewing (Buss 1998;Kirkpatrick 2000). Sulke teorieë versterk die insig dat homoseksualiteit deel van menswees is.…”