It is hard to identify the basis of complex human sexual behavior. Environmental, genetic and hormonal factors have been studied. Thus, studies now seem to focus on the biological determinants for sexual orientation, rather than simply a genetic basis or a hormonal basis, etc.
A look at some of the science.
In 1991 Bailey and Pillard found that the sons of self reported ( a source for sampling error) homosexual fathers had the following outcomes:
Of the relatives whose sexual orientation could be rated, the following rates of homosexuality were reported:
52% (29/56) of identical (monozygotic) cotwins,
22% (12/54) of fraternal (dizygotic ) cotwins, and
11% (6/57) of adoptive brothers
9.2% non-twin biological siblings
This has led to some to conclude that gayness is non-genetic. They claim that if it were genetic, then, the rates for homosexuality for brothers should approach that for fraternal and identical twins. Fair enough.
Yet, how does one explain that for the four groups of sons, of self reported homosexual fathers, given a base line rate of 9.2% to 11%, that the rate for fraternal and identical twins is 22% and 52%?
Certainly, one cannot discount that sons of gay fathers, who are identical twins, have a greater than 50% chance of concordance, that means, that if one of the identical twins is gay, the other has a 52% likelihood of being gay as well?
Doesn’t this show genetic linkage to homosexuality between identical twins? There is not much in science that has a 50% chance of concordance or greater. This is pretty strong data. It may not link homosexuality to a paternally heritable state, and in fact, the fraternal brothers high rate may reflect something in the maternal uterine environment, such as hormonal factors.
If, there was only an environmental factor, as some claim (2), then there should be a flat line of incidence, say, the 9.2% to 11% baseline rate.
Some current thinking on the multi variate causes for sexual orientation by Quinsey in 2003:
“People discover rather than choose their sexual interests. The process of discovery typically begins before the onset of puberty and is associated with an increase in the secretion of sex hormones from the adrenal glands. However, the determinants of the direction of sexual interest, in the sense of preferences for the same or opposite sex, are earlier. These preferences, although not manifest until much later in development, appear to be caused by the neural organizational effects of intrauterine hormonal events. Variations in these hormonal events likely have several causes and two of these appear to have been identified for males. One cause is genetic and the other involves the sensitization of the maternal immune system to some aspect of the male fetus. “
Some anti-gay bigots also claim that the change in category of homosexuality was not a reflection of heightened awareness and enlightenment by the psychiatric community, but rather, a caving in to the forces on the far left, i.e. the so called gay agenda.
So what does organized medicine have to say about this? This is a landmark article in the prestigious New England Journal of Medicine, 1994, that should ideally be available through gay activist groups and is preferred reading.
“The term homosexual entered common usage in 18693. The word gay, used to signify "homosexual," took on that meaning over the past 25 years in the context of the gay-rights movement. In common parlance, gay refers to males and sometimes to females, whereas lesbian is reserved exclusively for females.” (4)
Kinsey reported that 8 percent of men and 4 percent of women were exclusively homosexual for a period of at least three years during adulthood. Four percent of men and 2 percent of women were exclusively homosexual after adolescence
Subsequent studies of subjects more representative of the general population have yielded lower estimates of homosexual behavior8,9
Homosexuality may be underreported because of social prejudice.
Also, many homosexually arousable women may be included in the population reported as heterosexual, since women may engage in sexual intercourse without sexual arousal.
The term homophobia was coined in 1967 to signify an irrationally negative attitude toward homosexual people29. In the United States, two particularly prominent influences fostering antihomosexual attitudes have been religious fundamentalism and heterosexism, the belief in the moral superiority of institutions and practices associated with heterosexuality30.
Psychopathologic Issues
Independent studies with diverse designs have failed to find any increased frequency of various forms of psychopathology among homosexual people as compared with heterosexual people54
Ideally, complex developmental processes culminate in positive gay or lesbian identity and self-acceptance5. ...pathways leading to durable, loving sexual partnerships are common among lesbians and gay men16,75,76.
Many areas of law and public policy are still influenced by views discarded by behavioral scientists30,83,136. ...There are no data from scientific studies to justify the unequal treatment of homosexual people or their exclusion from any group.” (4)
In 2004 the Journal of PEDIATRICS published it’s report, which seems watered down and somewhat bowing to the pressure of right wing bigots. They failed to make a stand on whether homosexuality is a mental illness, rather, they danced around the social issues of modern life inherent to gay’ and straight teens:
This report reflects the growing understanding of youth of differing sexual orientations.
Health care professionals should provide factual, current, nonjudgmental information in a confidential manner.
All youths, including those who know or wonder whether they are not heterosexual, may seek information from physicians about sexual orientation, sexually transmitted diseases, substance abuse, or various psychosocial difficulties.” (5)
Most telling and somewhat disturbing is the tacit understanding, implied by this caveat to pediatricians, that not all healers among us are open minded, fair, non-judgmental and not bigoted, thus, they caution:
“Not all pediatricians may feel able to provide the type of care described in this report. Any pediatrician who is unable to care for and counsel nonheterosexual youth should refer these patients to an appropriate colleague.” (5)
Citations:
(1)Archives of General Psychiatry
Vol. 48 No. 12, December 1991
A genetic study of male sexual orientation
J. M. Bailey and R. C. Pillard
Department of Psychology, Northwestern University, Evanston, Ill 60208.
Homosexual male probands with monozygotic cotwins, dizygotic cotwins, or adoptive brothers were recruited using homophile publications.
Sexual orientation of relatives was assessed either by asking relatives directly, or when this was impossible, asking the probands.
Of the relatives whose sexual orientation could be rated,
52% (29/56) of monozygotic cotwins,
22% (12/54) of dizygotic cotwins, and
11% (6/57) of adoptive brothers were homosexual.
9.2% nontwin biological siblings
Heritabilities were substantial under a wide range of assumptions about the population base rate of homosexuality and ascertainment bias.
However, the rate of homosexuality among nontwin biological siblings, as reported by probands, 9.2% (13/142), was significantly lower than would be predicted by a simple genetic hypothesis and other published reports.
A proband's self-reported history of childhood gender non-conformity did not predict homosexuality in relatives in any of the three subsamples.
Thus, childhood gender nonconformity does not appear to be an indicator of genetic loading for homosexuality.
Cotwins from concordant monozygotic pairs were very similar for childhood gender nonconformity.
..............
(2)
http://salmon.psy.plym.ac.uk/year1/inttopic/homosexuality%20-%20an%20analysis%20of%20biological%20theories%20of%20causation.htmHOMOSEXUALITY - An Analysis of Biological Theories of Causation
(3) Annals of the New York Academy of Sciences 989:105-117 (2003)
The Etiology of Anomalous Sexual Preferences in Men
VERNON L. QUINSEY
Psychology Department, Queen's University, Kingston, Ontario, K7L 3N6, Canada
People discover rather than choose their sexual interests. The process of discovery typically begins before the onset of puberty and is associated with an increase in the secretion of sex hormones from the adrenal glands. However, the determinants of the direction of sexual interest, in the sense of preferences for the same or opposite sex, are earlier. These preferences, although not manifest until much later in development, appear to be caused by the neural organizational effects of intrauterine hormonal events. Variations in these hormonal events likely have several causes and two of these appear to have been identified for males. One cause is genetic and the other involves the sensitization of the maternal immune system to some aspect of the male fetus. It is presently unclear how these two causes relate to each other. The most important question for future research is whether preferences for particular-aged partners and parts of the male courtship sequence share causes similar to those of erotic gender orientation.
(4)
http://content.nejm.org/cgi/content/full/331/14/923The New England Journal of Medicine
Volume 331:923-930 October 6, 1994 Number 14
Homosexuality
Richard C. Friedman, and Jennifer I. Downey
(5) PEDIATRICS Vol. 113 No. 6 June 2004, pp. 1827-1832
CLINICAL REPORT
Sexual Orientation and Adolescents
Barbara L. Frankowski, MD, MPH and Committee on Adolescence
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