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Studies 1 & 2 into the causes of homosexual orientation

Quotes. Overview. More detailed coverage of 2
studies based on fingerprints & finger lengths

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Conflicting quotes:

  • "Nobody in science now believes that sexual orientation is caused by events in adolescence ... Homosexuality is an early, probably prenatal and irreversible preference."  Author and geneticist Matt Ridley 1

  • "Often, one's 'homosexuality' is thrust upon him by childhood molestation, poor familial relations, or general peer harassment during the adolescent years, including the continual calling of that child 'gay'." Parents Rights Coalition, a conservative Christian agency in Massachusetts. 2

  • "The only choice involved with being gay is when a person decides between living in the closet and hiding behind a facade, or deciding to accept, acknowledge and BE who they are." Author Kevin Schattenkirk, who is himself gay. 3

  • "Homosexuals... tell of rejection from early childhood and lack of bonding to same-sex parents, sexual violence and rape, or mental and emotional abuse as critical elements in the formation of their gender-identity" From a joint advertisement by the American Family Association, Christian Coalition, Concerned Women for America, Family Research Council, and many other conservative Christian groups. 4
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Conservative religious information sources generally reject the belief that homosexuality is caused or set up by genes. Information sources sponsored by gays, lesbians, religious liberals, mental health professionals and human sexuality researchers generally stress the genetic cause of sexual orientation.

In this section of our web site, we have described a number of research studies which show that the propensity towards homosexuality is traceable either to:

  • Genetic causes at conception, or

  • Environmental causes in the womb before birth.

We are always watching for new studies into this phenomenon. We have found none that contradict the above conclusions.

We continue to be on the lookout for research studies which indicate that homosexual orientation is not caused by genes, but have been unable to find any. If you locate any please email us the URL or other citation. See the "contact us" at the bottom of the page.

A number of studies on identical twins have indicated that perhaps 10% of people are born with the genetic predisposition to develop a homosexual orientation in adulthood. However, this predisposition may or may not be triggered, either before birth or during early childhood by a factor in the embryo's, fetus' or child's environment which is currently unknown. Thus, having a homosexual orientation is not completely determined by one's genes. However, current evidence is that it is certainly outside of a person's conscious control. Child psychologists can study 5-year-old children and predict with about 85% accuracy which ones will become lesbian or gay adults.

Religious conservatives generally reject these studies. They deny that people are set up by their genes to develop a homosexual orientation. They generally believe that gays and lesbians choose their orientation. One psychologist, Joseph Nicolosi, who is the president of the National Association of Research and Therapy of Homosexuality (NARTH) teaches that:

  • Homosexuality can be prevented by proper upbringing of children, and

  • Adults with a homosexual orientation can become heterosexual through therapy. 5

This theme has been picked up by the fundamentalist Christian group, Focus on the Family. Focus held "Love won out" conferences across North America for many years. They taught that "homosexuality is preventable and treatable." They have since abandoned these conferences. The same beliefs are also taught by many other conservative Protestant information sources. 6

Perhaps the most active conservative Christian group advocating therapy to change the sexual orientation of lesbians and gays was Exodus International. After over three decades of trying to change clients' sexual orientation they finally had to admit defeat. They were successful in convincing some gays and lesbians to become sexually inactive. They convinced some bisexuals to seek relationships only with persons of the opposite sex. But that was all. They reversed their beliefs about changing clients' sexual orientation, abandoned reparative therapy, apologized for their three decades of harm to the LGBT community and went out of business in mid-2003.

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Prejudice against gays and lesbians: 

Many people believe that prejudice against gays and lesbians will melt away if the public were to accept the belief that a person's sexual orientation is mainly determined by genes. The rationale is that if a person is a gay or lesbian because of their genetic makeup, then their orientation is not a choice; it is something beyond of their control. This belief appears to be contradicted by a 1999-APR web-site poll conducted by It dealt with "Genetics and Homosexuality," and asked the question: "Would your attitude towards homosexuality change if it were proven to be genetically determined?" Response as of 2000-MAR-6 was: 75% no, 21% yes and 4% not sure.

Also consider that:

  • The public has known for centuries that skin color is determined genetically, yet North America still has many racists who automatically hate or consider inferior anyone whose skin color falls within a certain range.

  • The public has known for centuries that the sex of a person is determined genetically, yet North America still has many sexists who denigrate women and attempt to restrict them to pre-defined roles in church and family.

  • Conservative Protestants typically have an unshakable belief that the authors of the Bible were inspired by God and that they produced inerrant text. Further, many interpret the six or seven "clobber passages" in the Bible that seem to touch on homosexual activity as implying that everyone is naturally heterosexual. They are unlikely to alter their beliefs, just because a series of scientific studies indicate otherwise.

  • In contrast, the Roman Catholic church teaches that sexual orientation is typically beyond a person's control It is neither changeable nor chosen by the individual; it is discovered. However, the church still urges governments and its own members to deny some human rights to gays and lesbians, like the right to marry the person that they love and to whom they are committed.

  • Liberals from all religions generally accept the findings of scientific studies which point to homosexual orientation as caused by genes.

  • The conservative wings of non-Christian religions still generally believe and teach that homosexuality is a chosen, unnatural behavior.
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Study #1, based on fingertip ridges:

J.A.Y. Hall and D. Kimura at the University of Western Ontario at London ON Canada found a relationship between the number of fingertip ridges on men and their sexual orientation. 7 They compared the number of ridges on the index finger and thumb of the left hand with the number on the corresponding fingers of the right hand. They found that 30% of the homosexuals tested had a surplus of ridges on their left hand, whereas only 14% of the heterosexuals did. This is a particularly interesting finding, because fingerprints are fully formed in a fetus before the 17th week of pregnancy, and do not change thereafter, through birth, infancy, childhood, youth and adulthood. This would seem to prove that for at least some adult homosexuals, their sexual orientation was pre-determined before birth, perhaps at conception, and certainly by the end of the 4th month of pregnancy. 8,9

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Study #2, based on finger-lengths:

A California psychologist, Marc Breedlove, "conducted his research at three street fairs in the San Francisco Bay area in the fall of 1999." Each study participant had his or her hand photocopied on a portable copy machine to record finger length. Participants also filled out a questionnaire on sexual orientation and birth order. 720 volunteers participated. They found that lesbians tended to have shorter index fingers (relative to their ring fingers) than did heterosexual women. They also found that gay males tended to have shorter index fingers (relative to their ring fingers) than heterosexual males. The relative size of a person's fingers is determined well before birth. These findings imply that sexual orientation is at least partly decided before birth -- perhaps at conception when a person's unique DNA is established. 10

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More studies are described 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. Matt Ridley, "Nature via nurture: Genes, experience, and what makes us human," HarperCollins, (2003). Page 159. Read reviews or order this book safely from online book store.
  2. "Statement on Homosexuality," Parents Rights Coalition, 2000-MAY-21, at:
  3. Kevin Schattenkirk, "Being gay - A choice? Debunking some popular views on homosexuality," The Daily University of Washington, 1999, at: (No longer available online)
  4. "Toward a new national discussion of homosexuality," Focus on the Family, 1998-SEP-15, at:
  5. Joseph and Linda Nicolosi, "A parent's guide to preventing homosexuality," InterVarsity Press, (2002). Read reviews or order this book safely from online book store. This book has been given a poor rating (2 stars out of 5) by reviewers.
  6. "Love won out," Focus on the Family," at:
  7. Caleb Crain, "Did a germ make you gay," Out magazine, 1999-AUG, Pages 46 to 49.
  8. Anne Moir and David Jessel, "Brainsex", Dell Books (1993)
  9. Dean Hamer & Peter Copeland "The Science of Desire: The Search for the Gay Gene & the Biology of Behavior", Simon & Schuster (1994)
  10. "Male hormone levels in womb may affect sexual orientation, study says," Health, 2000-MAR-29, at:
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Copyright 1997 to 2014 by Ontario Consultants on Religious Tolerance
Latest update: 2014-JUL-22
Author: B.A. Robinson

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