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Study 16 into the cause(s) of sexual orientation

Part 2: More detailed coverage of a conclusive
study of
identical twins separated at birth.
Conclusions by evangelical Christians

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This topic is continued from the previous essay

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Typical reasoning by religious conservatives:

Fundamentalists and other Evangelical Christians generally attribute the cause of homosexuality to some element in the person's upbringing. They expected this for at least two reasons:

  • Most believe that God is intimately involved in every event in one's life. This naturally includes each conception. If homosexuality were genetic, then God must intentionally create about one in twenty pre-embryos as gay or lesbian. However, since religious conservatives generally believe that God hates homosexual behavior, it makes no sense that he would intentionally create homosexuals.

  • If homosexuality is genetic, then it would probably be impossible to change. But many interpret 1 Corinthians 6 as showing that change is possible. Thus, they reason that homosexuality cannot be genetic.

Conservative Christian writers seem to have copied their beliefs on the identical twin study from fellow Christians rather than researching scientific literature. Some examples of their writing are listed below.

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Comments from Focus on the Family publications:

We start with three quotations from Focus on the Family -- a fundamentalist Christian advocacy group that has taken a particularly leading role -- particularly in the past -- to oppose equal rights for lesbians, gays, bisexuals, transgender persons and transsexuals:

  • In a Focus on the Family publication. author Mike Haley wrote:

    "So, if the study showed that homosexuality in [identical] twins was purely genetic, then both of the twins would have been homosexual 100% of the time." 1

  • James Dobson, founder of Focus on the Family, wrote in a 2002-JUN family newsletter that if homosexuality is genetically determined:

    "...since identical twins share the same chromosomal pattern, or DNA, the genetic contributions are exactly the same within each of the pairs. therefore, if one twin is 'born' homosexual then the other should inevitably have that characteristic too." 2

  • James Dobson also wrote in his Family Reference Guide:

    "...if it were specifically a genetic influence, then all identical twins would either have it or not have it. Their genes are exact duplicates, so anything deriving specifically from their DNA would express itself identically in the two individuals." 3

These statements are particularly unexpected because James Dobson -- the founder of Focus on the Family and its leader at the time these statements were published -- has a degree in child psychology. Thus, one would expect that he is very familiar with the workings of genes. Genetics would have formed a major part of his academic courses. In particular, one would expect that he would know that alleles (variations) of various genes have a penetrance (effectiveness) factor that is often much less than 100%.

Still, there is no evidence that he is aware of his error or that he is intentionally trying to deceive his audience. His academic training occurred many decades in the past; he may have simply forgotten how genes work.

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Comments from other conservative Christian groups about identical twin studies:

  • Kerby Anderson wrote an article for Probe Ministries. He wrote:

    "...why aren't nearly all identical twin brothers of homosexuals also homosexual? In other words, if biology is determinative, why are nearly half the identical twins not homosexual?" 4

  • Daniel R. Heimbach wrote:

    "Identical twins have identical constitutions, but one may become homosexual while the other is firmly heterosexual." 5

  • Sue Bohlin wrote:

    "Others ask, What about the identical twins where only one is gay? If sexual orientation is genetic, how do you explain the twins with such divergent orientations?" 6

  • N. E. Whitehead wrote an article for the National Association for Research and Therapy of Homosexuality (NARTH). They teach that homosexuality is a disordered state that is abnormal, unnatural, and changeable via reparative therapy. He wrote:

    "If homosexuality was a biological condition produced inescapably by the genes (e.g. eye color), then if one identical twin was homosexual, in 100% of the cases his brother would be too." 7

  • Rich Nathan has authored a fascinating book in which he discusses individuals who are (in his opinion) rejected by evangelicals : postmodernists, feminists, gays, lesbians, New Agers and religious liberals. He writes:

    "If biology (and not family structure or other environmental causes) really determined a person's sexual orientation, then identical twins ought to have a 100 percent concordance rate, since they are genetically identical. The 52 percent concordance rate actually argues against the notion of biological determinism and suggests other factors have influenced sexual orientation." 8

  • Dallin H. Oaks, a member of the Quorum of the Twelve Apostles of the LDS (Mormon) church wrote a definitive article in the magazine Ensign, titled "Same Gender Attraction." He wrote:

"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. 9 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).10 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." 11

  • Joe Dallas is an evangelical author who has written extensively about homosexuality. In the book titled "The Complete Christian Guide to Understanding Homosexuality" that he wrote with Nancy Heche, they discuss an identical twin study, writing:

    "Pillard and Bailey' suggested that the higher incidence of shared homosexuality among identical twins meant that homosexuality was genetic in origin. But this suggestion, like LeVay's, had its problems.

    Pillard and Bailey's findings actually indicate that something besides genes must account for homosexuality. If 48 percent of identical twins who are closely linked genetically, do not share the same sexual orientation, then genetics alone cannot account for homosexuality." 12

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This topic continues in the next essay

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References used:

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. "Family News from Dr. James Dobson," June 2002.
  3. James Dobson, "Complete Marriage and Family Reference Guide," Tyndale House, (2002), Page 402. Read reviews or order this book safely from online book store
  4. Kerby Anderson, "Homosexual Theology," at:
  5. 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:
  6. Sue Bohlin, "A Christian perspective on homosexuality," at:
  7. N. E. Whitehead, "The Importance of Twin Studies," NARTH, at:
  8. Rich Nathan, "Who is my enemy? Welcoming people the church rejects," Zondervan, (2002) Page 185. Read reviews or order this book safely from online book store
  9. J. M. Bailey & R. C. Pillard, "A Genetic Study of Male Sexual Orientation," Archives of General Psychiatry 48 (1991): Pages 1089 to 1096.
  10. 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.
  11. Dallin H. Oaks, "Same-gender attraction," Ensign, 1995-OCT, Pages 7 to 14.
  12. book cover image Joe Dallas & Nancy Heche, "The Complete Christian Guide to Understanding Homosexuality: A biblical and compassionate response to same-sex attraction," Harvest House Publishers, (2010), Page 183. Read reviews or order this book safely from online book store Available online at:
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Latest update: 2014-JUL-22
Author: B.A. Robinson

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