Is male homosexuality maintained via kin selection?

doi:10.1016/S1090-5138(01)00074-5

Evolution and Human Behavior

Volume 22, Issue 5, September 2001, Pages 361-368

https://doi.org/10.1016/S1090-5138(01)00074-5 Get rights and content

Abstract

We tested the kin selection hypothesis of male homosexuality using questionnaire data in a community sample of homosexual and heterosexual men. Homosexual men were no more likely than heterosexual men to channel resources toward family members. Indeed, heterosexual men tended to give more financial resources to siblings than homosexual men. Furthermore, homosexual men were somewhat more estranged from family members, especially from fathers and oldest siblings.

Introduction

Homosexuality is a paradox for evolutionary theory. Empirical studies have found a relatively low rate of direct reproduction by homosexual men Bell & Weinberg, 1978, Curran & Parr, 1957, Parr, 1957, Saghir & Robins, 1973. The persistence of a trait that drastically lowers fertility requires explanation. The evolutionary paradox is compounded by studies suggesting that at least a portion of the variance in sexual orientation can be accounted for by heredity Bailey et al., 2000, Bailey & Pillard, 1991.

Several sociobiological models have been proposed to explain homosexuality, although little data have been collected to test them. This paper describes the kin selection or inclusive fitness hypothesis, and then presents data relevant to testing the hypothesis.

Section snippets

Kin selection hypothesis

Wilson (1975), attributing the theory to Trivers and Spieth, first hypothesized that homosexual men reproduce not directly, but indirectly, through aid given to relatives. He likened this to the “sterile caste” in insects; adults who were freed from the need to expend energy on direct reproduction channel resources toward their kin, giving their families a special advantage.

In an elaboration of the hypothesis, Ruse (1982) and Weinrich (1976) suggested that in evolutionary history, gay men

Subjects

Heterosexual subjects were recruited using advertisements in a free urban alternative publication. The advertisements stated that heterosexual males or females aged 20–40 were desired for a study of personality, cognitive abilities, interests, and sexual behavior. (Females were part of a different study.) Homosexual subjects were recruited using nearly identical advertisements in gay publications. The final sample included 57 heterosexual and 66 homosexual men. Subjects were paid a nominal fee.

Reliabilities

Table 1 contains the internal consistency reliabilities (α's) of the four scales, for each group. Reliabilities were moderate to high.

Family Relationship Scales

Table 1 shows the mean rating-scale value for each of the four Family Relationship Scales. Rating-scale values are from 1 to 7, with lower number indicating greater effect. Scales measured proband's general feeling of closeness to family (General Affinity), tendency to give resources to family (Generosity), tendency to receive resources from family (Neediness),

Discussion

Contrary to predictions from the kin selection hypothesis of male homosexuality, we found no evidence that gay men are generous to their relatives. More specifically, gay men and heterosexual men were similar on scales measuring General Affinity, Generosity, Neediness, and Avuncular Tendencies. Indeed, on some specific questions, such as feelings toward fathers and oldest siblings, gay men were somewhat more emotionally distant.

Our questionnaire results contrast with the impression generated by

Acknowledgements

We thank Mark W. Jacobson for his help with statistical analysis and comments on the manuscript.

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As such, one prediction of the kin selection hypothesis is that androphilic males should be more willing to behave altruistically towards their close relatives (e.g., nieces and nephews) when compared to gynephilic males. However, research conducted on cisgender androphilic males in Euro-American (i.e., USA: Bobrow & Bailey, 2001; Canada: Abild, VanderLaan, & Vasey, 2014; Forrester, VanderLaan, Parker, & Vasey, 2011; UK: Rahman & Hull, 2005; Spain and Italy: Camperio Ciani, Battaglia, & Liotta, 2016) and non-Euro-American (Japan: Vasey & VanderLaan, 2012) industrialized cultures has not found evidence of a significant difference between androphilic and gynephilic males' willingness to engage in kin-directed altruism. In contrast, a program of research conducted on transgender male androphiles in Samoa has repeatedly found support for the kin selection hypothesis.
Male androphilia (i.e., sexual attraction and arousal to adult males) is considered an evolutionary puzzle because it reduces direct reproduction, but is influenced by genetic factors, reliably occurs across cultures, and has persisted over evolutionary time. The kin selection hypothesis states that genes for male androphilia can be maintained in a population if the costs of not reproducing directly are offset by enhancing the reproduction of kin. We tested this hypothesis among the Istmo Zapotec of Oaxaca, Mexico, where transgender and cisgender androphilic males are known as muxe gunaa and muxe nguiiu, respectively. We compared altruistic tendencies towards kin and non-kin children between muxe nguiiu (n = 106), muxe gunaa (n = 106), gynephilic men (i.e., men sexually attracted and aroused to adult females; n = 172), and androphilic women (n = 130). We also assessed whether the sisters of muxes (n = 96) reported receiving more childcare support from their muxe sibling compared to women with only gynephilic brothers (n = 65). The results showed that cisgender and transgender muxes reported more kin-directed altruistic tendencies than men. Muxe nguiiu also reported more kin-directed altruistic tendencies than women. When controlling for altruistic tendencies towards non-kin children, both muxe types exhibited more kin-directed altruistic tendencies than men and women. Women with muxe siblings reported receiving more childcare support from these relatives compared to women with only gynephilic brothers. These findings provide support for the kin selection hypothesis and highlight its potential role in elucidating the evolutionary paradox of male androphilia.
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In a similar vein, Ruse (1981) and Weinrich (1976) argued that the benefits to kin may come through sharing of income, bequeathing of wealth after death, and helping with child rearing. Empirical evidence however, does not support this hypothesis as several studies find that homosexual men are no more likely than heterosexual men to help their genetic relatives (Bobrow & Bailey, 2001; Rahman & Hull, 2005; VanderLaan & Vasey, 2012; see however, Vasey & VanderLaan, 2010). Another hypothesis sees same-sex attraction as the product of parental manipulation, where parents maximize their inclusive fitness by manipulating some of their children to become homosexual in order to provide support and assistance to other relatives (Ruse, 1988; Trivers, 1974).
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Is male homosexuality maintained via kin selection?

Abstract

Introduction

Section snippets

Kin selection hypothesis

Subjects

Reliabilities

Family Relationship Scales

Discussion

Acknowledgements

Genetic and environmental influences on sexual orientation and its correlates in an Australian twin sample

Journal of Personality and Social Psychology

A genetic study of male sexual orientation

Archives of General Psychiatry

Homosexualities: a study of diversity among men and women

Birth order and sibling sex ratio in homosexual versus heterosexual males and females

Annual Review of Sex Research

The evolution of desire: strategies in human mating

Homosexuality: an analysis of 100 male cases seen in private practice

British Medical Journal

Wilson's panchreston: the inclusive fitness hypothesis of sociobiology re-examined

Is the “North American berdache” merely a phantom in the imagination of western social scientists?

Sexual behavior in the human male

The evolution of human homosexual behavior

Current Anthropology