Homosexuality and bisexuality

Is homosexuality genetically determined?

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If the root cause of a homosexual orientation is genetic, as it is for Class 1 (early onset diabetes) and left-handedness, then the person will probably be unable to change their sexual orientation. As adults, they may decide to remain sexually inactive. However, their sexual attraction to persons of the same sex will continue.

If the root cause of a homosexual orientation is something in the environment, then there might be a significant chance that the individual can change their orientation through therapy. Many religious and social conservatives believe that incompetent parenting and/or child sexual abuse can cause a person to develop a homosexual orientation later in life.

Whether homosexuality is within or beyond the ability of a person to change may well influence people's attitudes towards homosexuality. It would certainly help homosexuals decide whether to try to change their orientation through reparative therapy in spite of the near zero success rate, cost, time, agony, and danger of extreme depression and suicidal ideation.

An article in The Advocate, a gay-positive magazine states:

"Polls repeatedly indicate that Americans who believe sexual orientation is either genetic or biological are much more likely to support gay and lesbian civil rights than those who believe it is determined primarily by environmental influences." ₁₃

This may or may not be an accurate conclusion. Religious and social conservatives are generally opposed to equal rights for sexual minorities, and believe on biblical grounds that sexual orientation is a decision made after puberty -- perhaps triggered by incompetent parenting or childhood sexual abuse. Those who favor gay, lesbian, bisexual and transsexual rights tend to base their beliefs more on scientific findings and less on holy texts. So the root cause of support for equal rights for all might be more related to religious beliefs than beliefs about the cause of homosexuality. Besides, race has been known for centuries to be genetically determined. Yet this knowledge has not eliminated racial bigotry.

Why it is so question controversial:

This topic has triggered many angry Emails from visitors to this web site:

Evidence seems to point consistently to a genes as the root cause which either lies dormant or is triggered into causing the individual to have a homosexual orientation later in life. Such a finding makes many people -- both religious conservatives and homosexuals -- angry because their cherished beliefs are disproved. Some direct that anger at us because we report the information. Fortunately, we have developed very thick skins at this job.

The identical twin evidence:

Essentially all conservative Christian authors who have written about homosexuality maintain that sexual orientation is not determined by one's genes. Most treat it as an abnormal, unnatural, chosen, and changeable habit or addiction. Religious conservatives often point to studies of identical twins who were separated at birth and raised independently. If one is gay, then the other twin is found to be gay only about 55% of the time. They reason that: since identical twins have the same genetic structure, then if homosexual orientation were determined by genes, 100% of the other twins would be gay. Thus they conclude that homosexual orientation is not genetically caused.

Many gays and lesbians believe that their orientation is caused by their genes; it is normal, natural, unchosen and unchangeable. With the exception of one small religious association of therapists, the vast majority of human sexuality researchers and mental health therapists accept that the root cause of homosexual orientation is genetic.

The data seems to show that a small minority of individuals -- perhaps 10% -- have a "gay gene" or sequence of "gay genes." However, the gene is only expressed in perhaps 55% of those individuals, as a result of some unknown factor in the environment. In the remainder, it remains dormant and the person matures as a heterosexual.

Typical conclusions of religious conservatives:

Fundamentalists and other Evangelical Christians generally attribute the cause of homosexuality to some element in the person's environment. This is to be expected for at least two reasons:

Conservative Christian writers seem to have copied their beliefs from fellow Christians rather than researching scientific literature. Some examples of their writing:

"A study of fifty-six pairs of identical male twins in which one twin classified himself as "gay" reported that 52 percent of the co-twins also classified themselves as gay. ₁₄ A similar study of female identical twins yielded approximately the same proportion of co-twins who classified themselves as gay (thirty-four of seventy one pairs 48 percent).₁₅ If these studies show some inherited influence on whatever causes a man or woman to classify himself or herself as homosexual or lesbian, it is clear that this influence is not determinative. As a prominent scientist observed, "Even the identical twin of a gay man has a 50 percent or more chance of being heterosexual--even though he has the exact same genes and is reared by the same parents." ₁₆

Religious conservatives often attribute the cause of homosexuality to:

One logical result from this belief is that sexual orientation should be changeable through adult therapy for at least some gays and lesbians. Thus, we see many conservative Christian groups promoting reparative therapy and/or transformational therapy, which attempt to convert gays and lesbians into heterosexuals through prayer and counseling.

One exception is God's Rainbow. They conclude that genes cause some gays and lesbians to develop a homosexual orientation. They feel that other homosexuals develop a same-sex attraction because of elements in their early environment. They give the familiar explanation that genetics are not the complete cause of homosexuality, reasoning that: "...since identical twins have exactly the same genetic code, one would expect a 100% correlation in their sexual orientation. When one identical twin is gay / lesbian, the other should be too." They conclude that some people develop a homosexual orientation because of genetic causes; others because of a factor in their early childhood. The latter would presumably be treatable with therapy.

Typical conclusions of geneticists:

Many genetics researchers, and other investigators who are not religious conservatives, examine the data from various studies and have concluded that the conclusion of most religious conservatives is wrong. Studies prove that homosexuality is not caused by poor parenting or child molestation, alone. This is easily verified. Consider two identical newborn twin boys who were separated at birth and raised in different homes without any contact with each other. If homosexuality were caused by something in the environment, then, if twin #1 turned out to be gay, the chances of the other twin becoming a gay adults would only be about 5%. That is because the second twin would have been exposed to a totally different environment during his upbringing. So his chances of being gay  would be the same as for any other male -- about 5%. But, studies have reliably shown that if one twin is gay, there is about a 55% chance that the other twin will be gay.

One explanation which is popular among some religious conservatives is that homosexuality is in fact caused by demon possession. They often believe that demon possession can be passed on to all children in a family through generational curses created by the sin of a parent or grandparent. This belief is consistent with the findings of identical twin studies. However, very few people who are not religious conservatives believe in the existence of demons and the possibility of possession by evil spirits.

The rejection of a genetic cause of homosexuality by essentially all conservative Christians and some others seem to be based upon a faulty or inadequate knowledge of the detailed workings of genetics. Genes have a property called penetrance, which is a measure of their effectiveness, or power. Consider the gene for:

Sometimes, as in the case of Huntington's Disease, the presence to an allele is certain to cause the disease later in life. In most cases, some genetic combination only makes a person susceptible to a disease or disorder. It takes some factor in the environmental to trigger the disease into activity. Without that trigger, the disease never develops.

We do not wish to imply that homosexuality is a disease. We are merely suggesting that the root cause of many diseases -- and traits like left-handedness -- are genetic. Most human sexuality researchers who are not religious conservatives regard homosexual orientation as a trait like left-handedness.

One theory that fits the available observations is that the penetrance of the "gay gene(s)" is approximately 67%. That causes about half of the males with the gene(s) become gay. "There could be hundreds of millions of straight men walking around with this gay allele but who are straight simply because it didn't penetrate" In the case of the "gay gene(s)" perhaps 10% or more of all males have the allele that causes homosexuality, but in many cases is the allele not "triggered." 

Assuming that the penetrance of the "gay gene" or "gay genes" is 67%, then one would expect that if one fraternal twin was gay that the other would also be gay about 22% of the time. This number also agrees with studies of families with fraternal twins.

Nobody knows what triggers the allele. It might be some event happening in the womb, like an abnormal amount or irregular timing of hormones. It might be some event during early childhood -- before school age. Either way, it is outside the control of the individual and his family of origin. What is known is that it takes effect before the child reaches age 5. Child psychologists can interview children at that age and determine with excellent accuracy who will grow up to be gay.

Related essays:

References:

The following information sources were used to prepare and update the above essay. The hyperlinks are not necessarily still active today.

1. Mike Haley, "Straight Answers: Exposing the myths and facts about homosexuality," Focus on the Family, Love Won Out series, (2000), Page 9.
2. Kerby Anderson, "Homosexual Theology," at: http://www.probe.org/
3. Daniel R. Heimbach,  "Notes for The Bible in the Moral War over the Rejection of Homosexuality by the Military Services: A View from Inside the Pentagon," PREMISE, Volume II, Number 7, 1995-AUG-27, Page 10. Online at:  http://capo.org/premise/95/august/
4. Sue Bohlin, "A Christian perspective on homosexuality," at: http://www.northave.org/
5. N. E. Whitehead, "The Importance of Twin Studies," NARTH, at: http://www.narth.com/
6. "Family News from Dr. James Dobson," June 2002.
7. Rich Nathan, "Who is my enemy? Welcoming people the church rejects," Zondervan, (2002) Page 185. Read reviews or order this book safely from Amazon.com online book store
8. "Brothers and Twins," 1997-OCT, at: http://www.geocities.com/
9. Sylvia, "The Biological Basis of Homosexuality," at" http://www.geocities.com/southbeach/
10. James Dobson, "Complete Marriage and Family Reference Guide," Tyndale House, (2002), Page 402. Read reviews or order this book safely from Amazon.com online book store
11. Louis Rosner & Shelley Ross, "Multiple Sclerosis: Updated edition," Simon & Schuster, (1992), Pages 7 - 15. Read reviews or order this book.
12. "Strong genetic component to Schizophrenia," Undated, at: http://www.schizophrenia.com/
13. David Mubarak, "Why are we gay? -- opinions and research," The Advocate, 2001-JUL-17, at: http://www.findarticles.com/
14. J. M. Bailey & R. C. Pillard, "A Genetic Study of Male Sexual Orientation," Archives of General Psychiatry 48 (1991): Pages 1089 to 1096.
15. J. M. Bailey & R. C. Pillard, et al., "Heritable Factors Influence Sexual Orientation in Women," Archives of General Psychiatry 50 (1993), Page 217 to 223.
16. Dallin H. Oaks, "Same-gender attraction," Ensign, 1995-OCT, Pages 7 to 14.