Is homosexuality familial? A review, some data, and a suggestion

An Ethological Perspective on Homosexuality during Adolescence

An ethological perspective is presented as an alternative to traditional developmental approaches to adolescence. From an evolutionary point of view, the onset of reproductive capability during adolescence marks the significance of this time during the life course. Thus, the apparent anomaly of male and female youth "preferring" not to engage in heterosexual activities that have the potential to maximize genetic fitness but to participate in homosexual activities that do not have the same adaptive repercussion poses a challenge for an ethological perspective to interpret. To better understand an ethological perspective, basic ethological principles are applied to the emergence and expression of homosexuality during adolescence. First, evidence bearing on the genetic etiological under-pinnings of homosexuality within humans is reviewed through an examination of (a) behavioral genetic studies and (b) hormonal research. Next, adaptive considerations are presented, in particular the prevalence of homosexual behavior among various animal species and human societies, as well as evolutionary pressures that maintain a stable level of homosexuality in the human population. Balanced polymorphism and kin selection are reviewed as answers to the ultimate or functional question. Finally, the "naturalness" of adolescent homosexuality as an outcome of an ethological perspective is proposed. Homosexuality is thus presented as a sexual orientation that is not so much a matter of choice but of biological necessity.

The Body As Crowbar

Can paradoxical or ambiguous sexual identities and practices change, or even go beyond, the meanings of masculinity and femininity? In other words: can the body be a source of social change? To answer this question I turn to the work of two theorists: Luce Irigaray and Judith Butler. After an account of their ideas, various sexual practices and identities will be described. The question is whether these practices and identities affect the meanings of masculinity and femininity. It will be concluded that, even in our postmodern world with its technological opportunities the division into the two sexes is extraordinarily persistent. However, we can expect some change from the extension of the categories of masculinity and femininity, rather than from attempts to break free from them altogether.

Perinatal administration of aromatase inhibitors in rodents as animal models of human male homosexuality: similarities and differences

In this chapter we briefly review the evidence supporting the existence of biological influences on sexual orientation. We focus on basic research studies that have affected the estrogen synthesis during the critical periods of brain sexual differentiation in male rat offspring with the use of aromatase inhibitors, such as 1,4,6-androstatriene-3,17 (ATD) and letrozole. The results after prenatal and/or postnatal treatment with ATD reveal that these animals, when adults, show female sexual responses, such as lordosis or proceptive behaviors, but retain their ability to display male sexual activity with a receptive female. Interestingly, the preference and sexual behavior of these rats vary depending upon the circadian rhythm.Recently, we have established that the treatment with low doses of letrozole during the second half of pregnancy produces male rat offspring, that when adults spend more time in the company of a sexually active male than with a receptive female in a preference test. In addition, they display female sexual behavior when forced to interact with a sexually experienced male and some typical male sexual behavior when faced with a sexually receptive female. Interestingly, these males displayed both sexual behavior patterns spontaneously, i.e., in absence of exogenous steroid hormone treatment. Most of these features correspond with those found in human male homosexuals; however, the "bisexual" behavior shown by the letrozole-treated rats may be related to a particular human population. All these data, taken together, permit to propose letrozole prenatal treatment as a suitable animal model to study human male homosexuality and reinforce the hypothesis that human sexual orientation is underlied by changes in the endocrine milieu during early development.

The relationship between socioeconomic factors, wellbeing, and homosexuality in the theatrical profession

This article relates to the theory suggesting that there is a prevalence of male homosexuality within the theatrical profession that can be explained through male performers becoming homosexual due to their low socioeconomic position. In a questionnaire-based study, the socioeconomic status (SES) is measured of 121 homosexual performers who considered themselves to have been heterosexual at the time of joining the profession, and results are compared with a control group of 121 heterosexual male performers. The experimental group was chosen in this way due to the suggestion of the hypothesis that the change in sexual orientation occurs after the man begins performing professionally. Results were not significant and little difference was noted in any of the parameters of SES, including annual earnings and home ownership. However, a marginal though insignificant increase in SES was noted in the experimental group of homosexual men. Consequently, existing theories for homosexuality and possible reasons for the high prevalence within the performing profession are discussed; the notions of adult performing and creativity being extensions of childhood gender atypical behavior are considered and possible links between sexual orientation and these traits. Elements of genetic heritability of homosexuality are likewise implicated.

Sexually antagonistic selection in human male homosexuality

Several lines of evidence indicate the existence of genetic factors influencing male homosexuality and bisexuality. In spite of its relatively low frequency, the stable permanence in all human populations of this apparently detrimental trait constitutes a puzzling ‘Darwinian paradox’. Furthermore, several studies have pointed out relevant asymmetries in the distribution of both male homosexuality and of female fecundity in the parental lines of homosexual vs. heterosexual males. A number of hypotheses have attempted to give an evolutionary explanation for the long-standing persistence of this trait, and for its asymmetric distribution in family lines; however a satisfactory understanding of the population genetics of male homosexuality is lacking at present. We perform a systematic mathematical analysis of the propagation and equilibrium of the putative genetic factors for male homosexuality in the population, based on the selection equation for one or two diallelic loci and Bayesian statistics for pedigree investigation. We show that only the two-locus genetic model with at least one locus on the X chromosome, and in which gene expression is sexually antagonistic (increasing female fitness but decreasing male fitness), accounts for all known empirical data. Our results help clarify the basic evolutionary dynamics of male homosexuality, establishing this as a clearly ascertained sexually antagonistic human trait.

Sequencing and its consequences: path dependence and the relationships between genetics and medicalization

Both advocacy for and critiques of the Human Genome Project assume a self-sustaining relationship between genetics and medicalization. However, this assumption ignores the ways in which the meanings of genetic research are conditional on its position in sequences of events. Based on analyses of three conditions for which at least one putative gene or genetic marker has been identified, this article argues that critical junctures in the institutional stabilization of phenotypes and the mechanisms that sustain such classifications over time configure the practices and meanings of genetic research. Path dependence is critical to understanding the lack of consistent fit between genetics and medicalization.

Genetic models of homosexuality: generating testable predictions

Homosexuality is a common occurrence in humans and other species, yet its genetic and evolutionary basis is poorly understood. Here, we formulate and study a series of simple mathematical models for the purpose of predicting empirical patterns that can be used to determine the form of selection that leads to polymorphism of genes influencing homosexuality. Specifically, we develop theory to make contrasting predictions about the genetic characteristics of genes influencing homosexuality including: (i) chromosomal location, (ii) dominance among segregating alleles and (iii) effect sizes that distinguish between the two major models for their polymorphism: the overdominance and sexual antagonism models. We conclude that the measurement of the genetic characteristics of quantitative trait loci (QTLs) found in genomic screens for genes influencing homosexuality can be highly informative in resolving the form of natural selection maintaining their polymorphism.

Male homosexuality: absence of linkage to microsatellite markers at Xq28

Several lines of evidence have implicated genetic factors in homosexuality. The most compelling observation has been the report of genetic linkage of male homosexuality to microsatellite markers on the X chromosome. This observation warranted further study and confirmation. Sharing of alleles at position Xq28 was studied in 52 gay male sibling pairs from Canadian families. Four markers at Xq28 were analyzed (DXS1113, BGN, Factor 8, and DXS1108). Allele and haplotype sharing for these markers was not increased over expectation. These results do not support an X-linked gene underlying male homosexuality.

The beliefs of members of the American Psychiatric Association on the etiology of male homosexuality: a national survey

This study is an analysis of psychiatrists' (N = 508) attitudes with regard to the etiology of male homosexuality. A random sample of members of the American Psychiatric Association revealed an endorsement of a biological perspective. Attitudes were further analyzed with regard to variation by school of thought, practice setting, and number of years practicing psychiatry.

Homosexuality, type 1: an Xq28 phenomenon

Despite the absence of phenotypic manifestations in alternating generations characteristic of X-linked disorders, a thesis is presented that a major type of Kinsey grades 5 and 6 male homosexuality is determined by a gene in the Xq28 region. A total of 133 families in 78 kinshps of male and female homosexual probands, in addition to 116 families (including those of 40 famous homosexuals) from the literature, revealed an unbalanced secondary sex ratio in the maternal generation of male, but not of female, homosexuals. On the maternal side, in this study, the ratio of all uncles to all aunts of 90 males homosexuals was 132/209, chi 2 = 8.52, p = 0.004. On the maternal side for the total of all sources, the ratio of uncles to aunts of male homosexuals was 241/367, chi 2 = 13.20; p < 0.0001. The male/female ratio of the total number of maternal sibships bearing homosexuals (310/628: 0.491) was a measure of fetal wastage of the mothers' male sibs; 49%. This ratio was very close to that of the total number of children born to fathers affected with any one of nine Xq28-linked male semilethal conditions (255/508: ratio 0.556); for the difference between the two populations chi 2 = 0.859, p = 0.354. The male/female ratio of the total number of children born to female carriers of any one of these same conditions (1,232/1,062: ratio 1.16), chi 2 = 13.8 p < or = 0.0001, is close to that of the total number of children in homosexual sibships: 511/413, chi 2 = 10.4, p = 0.005. Between the number of children born to Xq28 mothers and to those born of mothers of homosexuals chi 2 = 0.581, p = 0.446. One may readily surmise that the maternal influence so often related to homosexuality may lie in the mother being a genetic carrier, with traits thereto associated. In this study, 65% of the mothers of homosexuals had no or only one live-born brother. Additional support for a genetic hypothesis is found in the occurrence of multiple instances--almost exclusively among maternal relatives--of infertility, spontaneous abortions, miscarriages, stillbirths, remaining single past age 30, and suicide. Of 109 male and 43 female homosexual index cases in the present series there were 6 instances of brother/sister homosexual sibships.(ABSTRACT TRUNCATED AT 400 WORDS)

Psychoanalysis, psychobiology, and homosexuality

The potential role of biological influences in human sexual orientation was considered more seriously during the early phases of psychoanalysis than in the years since World War II. Recently studies of homosexuality and heterosexuality in the neurosciences have attracted widespread attention both in the scientific and lay communities. The salience of these new data for psychoanalytic theory and practice is just beginning to be explored. In this article, we review research on sexual orientation in the following areas: genetics, crosscultural studies, studies of development in individuals with abnormal prenatal hormone exposure, childhood play patterns, and brain studies in both nonhumans and humans. Differences between male and female homosexuality are explored. We propose that psychoanalytic theory can grow and profit from a careful consideration of new findings in the psychobiology of sexuality, and that the interaction between mind and body is the appropriate purview of psychoanalysis.

Sperm competition and the persistence of genes for male homosexuality

Homosexuality is increasingly recognized as having a genetic component. Why then does it persist, when common sense suggests that it should result in fewer offspring? Monozygotic-twin studies permit a rough estimate of the importance of genetics (70%) in the development of male homosexuality, and the proportion of homosexuals remains constant: Fisher's Theorem then tells us there is an advantage to the heterozygote, which we find need be no greater than 2%. Behavior and sperm competition suggest what this advantage might be.

Proportion of unmarried siblings of homosexual and non homosexual gender-dysphoric patients

Among the siblings of homosexuals, a lack of sexual and romantic interest in women may be independent of erotic feelings for men. This study investigated the sexual histories of siblings of gender-dysphoric outpatients. The patients were classified into three groups: non homosexual males, homosexual males and homosexual females. Their siblings consisted of 301 brothers and 284 sisters over the age of 25. Logistic regression showed that the brothers of the homosexual male patients were significantly less likely to have been married, either legally or common-law, than the brothers of the other gender-dysphoric groups, even with age and relative birth order taken into account. This finding suggests that the low propensity for long term heterosexual relationships seen in homosexual male gender-dysphoric patients also tends to appear in their brothers.

Theoretical perspectives accounting for adolescent homosexuality

Few topics in sexology elicit such a diversity of opinions and emotions as the question of etiology of homosexuality. Views frequently carry with them implicit or explicit messages concerning the psychologic health of this sexual orientation. Theories of sexual development usually portray adolescence as a critical time in the life course because of changes in: 1) anatomy and physiology; 2) psychologic functioning: the reawakening, renewal, and reliving of previously established sexual relations and drives; and/or 3) social conditions: an increased exposure and adherence to societal messages concerning appropriate and inappropriate social and sexual behaviors and relationships. This paper provides a brief overview of several major theories--evolutionary biology, psychoanalysis, and social processes--as they relate to the development of sexual orientation. In addition, an ethologic perspective that synthesizes various etiologic theories, as they relate to homosexuality during adolescence, is briefly reviewed. In these discussions, the issue of whether homosexuality is a normal or abnormal developmental state during adolescence is also addressed.

The periodic table model of the gender transpositions: Part II. Limerent and lusty sexual attractions and the nature of bisexuality

I propose a theory that puts the notion of two sexual attractions into a precise, testable form, and then I mesh it with the periodic table model of the gender transpositions described previously (Pillard & Weinrich, 1987). I define a limerent sexual attraction, active in eroticizing the physical and personality characteristics of a particular Limerent Object, and a lusty sexual attraction, active in producing erotic arousal when encountering a new Lusty Object. Three hypotheses then account for much of what we know about sexual orientation: (a) Limerence and lustiness are experienced by both men and women-but there is an average difference in the ease with which each can be elicited in a particular sex. Limerence is experienced by most women in our culture as an autonomously arising desire, whereas lustiness, when it occurs, is experienced mostly as a reaction to particular stimuli. Lustiness is experienced by most men in our culture as an autonomously arising desire, whereas limerence, when it occurs, is experienced mostly in reaction to particular stimuli. (b) In some people the limerent attraction can be indifferent (or nearly so) to the sex or gender of the Limerent Object. (c) The lusty attraction is rarely indifferent to the sex or gender of the Lusty Object. Individuals may vary in their readiness to respond to the two kinds of attraction. Some of this variability can be understood in the light of the periodic table model described previously, and some of it can be understood in the light of cultural conditioning and socialization. The result is a theory that deduces many of the major facts about sexual orientation from only a small number of hypotheses.

Penile malformation, gender identity and sexual orientation

Gender identity and sexual orientation were investigated in 34 men operated for hypospadias in childhood and in 36 matched control subjects. Independent psychiatric assessments from semi-structured interviews, and double-blind formalized psychological ratings from the Rorschach, yielded similar findings. The probands were less secure in their maleness but were similar in sexual orientation as compared to the controls. A third blind, independent measure of unconscious gender identity, the Franck Drawing Completion Test, gave further evidence of uncertain gender identity in the patients. A self-administered inventory, the Gough Femininity Scale, showed a tendency for the patients to take more feminine sex roles. The findings are discussed from psychoendocrinological as well as psycho-analytical view points. The need for early psychological preventive measures for hypospadic boys and their parents is stressed.

Biology of sexuality inborn determinants of human sexual response

Opinions vary on the relative importance of biological and learning processes in the aetiology of sexual expression and deviance. The structure of personality, consistency of fantasy patterns, and the familial nature of homosexuality hint at a biological anlage. Research with the HY-antigen complex and X chromosome, and the elucidation of the interactions of intrauterine testosterone and its products with the foetal brain and neurotransmitters, have given us new models to understand the programming of sexuality. However, gonadotrophin feedback is not relevant as an indicator of brain feminization in primates and man. Finally, the interaction of masculinization and defeminization provides us with a model for understanding homosexual behaviour.

A family study of sexual orientation

Unmarried men aged 25--35 were recruited through newspaper and radio advertisements for a family study of sexual orientation. Fifty predominantly homosexual and 50 predominantly heterosexual men comprised the index subjects. The test, questionnaire, and interview battery is described. Subjects were asked about the sexual orientations of their relatives. The homosexual index men report a significant excess of homosexual brothers and more distant male relatives but not of homosexual sisters or female relatives. Moreover, the percentage of homosexual brothers increases with the Kinsey rating of the index subjects. Overall, about 25% of brothers of homosexual men are reported also to be homosexual.