The Bible’s appraisal of male homosexuality is clear. Leviticus 20:13 states: “If a man also lie with mankind, as he lieth with a woman, both of them have committed an abomination: they shall surely be put to death; their blood shall be upon them.” It is not surprising that this sort of pronouncement sometimes leads to intolerance and in extreme cases to assaults and even murder.
In a study done at Kent State University on nursing students in 1999, researchers found there was a significant correlation between homophobia, frequency of church attendance, and Christian Orthodoxy.The Christian religion, especially the Catholic and the Fundamentalist Protestant branches, has contended that homosexuality is a sinful life-style choice, one that is voluntarily entered into, and one than can be abandoned if desired.
Unfortunately, I seldom hear individuals quoting scientific evidence but only biblical references and long held prejudices. Even my fellow physicians are often unaware of the scientific literature on this subject.
Sexual orientation refers to whether a person’s erotic desires are directed toward the same sex (homosexuality), the opposite sex (heterosexuality), or both sexes (bisexuality). A person’s actions may not always match his or her sexual orientation, such as when a person conceals his sexual orientation for practical reasons. In this discussion we will be focused on sexual orientation.
Seldom do we hear from psychiatrists and psychologists, who encounter homosexuals in their practices, or from scientific researchers. In 1973, on the basis of research findings, the American Psychiatric Association removed homosexuality as a disorder from their official manual, the Diagnostic and Statistical Manual of Mental Disorders. Their conclusion was: “The reality is that homosexuality is not an illness. It does not require treatment and is not changeable.” They further added: “There is no published scientific evidence supporting the efficacy of ‘reparative therapy’ as a treatment to change one’s sexual orientation.” In 1975, the American Psychological Association passed a resolution supporting the conclusions of the American Psychiatric Association. The World Health Organization passed a resolution in 1990 to remove homosexuality as a mental illness from its official manual. In 2000, the American Psychiatric Association reaffirmed its position of 1973 and stated that “in the last four decades, ‘reparative’ therapists have not produced any rigorous scientific research to substantiate their claims of cure.” In 2001, The United States Surgeon General, David Satcher M.D., issued a report maintaining that “there is no valid scientific evidence that sexual orientation can be changed.”
In considering the cause of homosexuality, there are three possibilities: environmental, intrauterine effects during pregnancy, or genetic.
First, let’s discuss the longstanding and firmly held belief that there is something different in the environment that causes a person to be gay. Sigmund Freud, Alfred Kinsey, William Masters, and Virginia Johnson held that homosexuality was socially learned. Bailey and Pillard, however, researchers that have published the most studies in the field, reviewed all the scientific evidence in 1991 in the Archives of General Psychiatry and concluded: “Previous attempts to test psychodynamic and psychosocial theories have largely yielded negative findings and emphasize the necessity of considering causal factors arising within the individual and not just his psychosexual environment.” This very cautiously phrased scientific statement is basically saying that these researchers reviewed all of the studies and the evidence for any environmental cause of homosexuality is lacking.
Although intrauterine influences are suggested as a factor in homosexuality by a few researchers, the limited amount of scientific evidence available is too fragmentary to determine if it is significant or not. Most of the scientific findings strongly favor a genetic origin. At any rate, sexual orientation is something that people are born with and is not acquired.
Evidence Supporting a Genetic Cause of Homosexuality:
Twin Studies.
Multiple twin studies have demonstrated a hereditary component to homosexuality. Monozygotic twins (ones from a single ovum) share exactly the same genes, whereas dizygotic twins (one from two different ova) share 50% of their genes, the same as any non-twin sibling). The number of gays in the U.S. Population is 3-4% for males and 1-2% for females.
Since monozygotic (also called identical) twins share identical genes, the chance of a match in sexual preference should be evident if heredity is operative. In the case of dizygotic (also called fraternal) twins, since only half the genes is shared, a figure of about one half of that for identical twins would be expected.
As examples, the results of two studies by Bailey and Pillard, are presented, but other twin studies have yielded similar results. One study was limited to males where it was revealed that if one identical twin was gay, the other was gay 52% of the time. If one fraternal twin was gay,the remaining twin was gay 22% of the time. In the other twin study, which was limited to females, if one identical twin was gay, the other one was also gay 48% of the time, and if one fraternal twin was gay, the other was also 16% of the time.
Even though the observation that the approximately 50% concordance in homosexuality in identical twins points to a strong heredity component, this figure could also suggest that genetics might not be the entire explanation. But this 50% figure is still consistent with genetics alone being the cause. Two examples of hereditary diseases in identical twins will show why.
If identical twins have the genes for Huntington’s Disease, both twins will develop the disease 100% of the time. However, if identical twins have the genes for Type 1 Diabetes, both will have only a 30% chance of developing the disorder. Therefore, even though identical twins have identical genes, the manifesting of the genes can vary, a process called variable penetrance, a phenomenon that is poorly understood at this time.
Animal Studies.
- Recent genetic studies on the geneticists’ favorite subject, the fruit fly (drosophila melanogaster), has provided valuable information to scientists about homosexuality. The fruit fly has a recognizable match with 75% of known human disease genes and has contributed valuable genetic information to scientists for almost 100 years. Manipulation of a single gene called “fruitless” induces homosexual behavior in either sex. Normally, a male fruit flies’ ritual for the seduction of the female fruit is dramatic and involves such maneuvers as tapping her with his foreleg, extending and vibrating his wings in song, and then brazenly licking her. This male sexual behavior is exactly reproduced in females with the manipulation of the “fruitless” gene. In another recent study on fruit flies, David Featherstone and coworkers discovered that a mutation in a gene they call “genderblind” turns fruitflies bisexual.
- Studies on animal sexual behavior have been revealing. Homosexual behavior has now been well documented in 500 animal species.
Anatomical and Physiological Differences in Gays.
These associated findings are further evidence that homosexuality is biological, something that people are born with. I’ll just list the differences since the list is long:
- Gays are 39% more likely to be left-handed than straight people.
- Men typically have a ring finger that is longer than the index finger, while in women the two are about the same length. Two studies have shown that in lesbians the ratios between the two fingers are similar to those in men.
- One study compared fingerprints in men of the thumb and index fingers. 30% of homosexuals had an excess of ridges on the left hand, whereas only 14% of heterosexuals did. This finding is particularly interesting since fingerprints are fully determined in a fetus before the 17th week of pregnancy and do not change thereafter throughout life.
- The startle response (eye blink following a loud noise) is masculinized in lesbians and bisexual women.)
- Gay and non-gay people emit different armpit odors.
- There are anatomical and physiological differences in the brain: The average size of the INAH-3 (a part of the hypothalamus) in the brains of gay men is approximately the same size as the significantly smaller one of women. The anterior commissure is larger in gay men than in non-gay men. Three regions of the brain (medial prefrontal cortex, left hippocampus, and right amygdala) are more active in gay men than non-gay men when exposed to sexually arousing material. Gay and non-gay brains respond differently to two human sex pheromones (AND, found in male armpit secretions, and EST, found in female urine).
Behavioral traits.
To varying degrees, gays often show characteristic behavior that appears to be a biological part of their nature. Gay males tend to show variable degrees of feminine behavior and lesbians variable degrees of masculine behavior, and these findings often are discernible in early childhood. Of course, in some cases gay individuals show behavior that is indistinguishable from heterosexuals.
Casual observers can often judge sexual orientation with very limited information. A 1999 Harvard study found that by simply looking at photographs of seated strangers that undergraduates could identify the sexual orientation accurately 55% of the time. In another study, 112 undergraduate observers saw only the backsides of subjects as they walked on treadmills. The observers correctly identified the sexual orientation of males with over 60% accuracy, but the categorization of women did not exceed chance. As another example of readily available behavioral clues to a person’s sexual orientation, a researcher, Gerulf Rieger shows videotapes of men and women discussing the weather, and observers are able to tell who is gay and who is straight with great accuracy. Rieger states that “even within seconds, people are pretty good at figuring out who’s gay and who’s not.” Rieger thinks his research points to genetics as the source of sexual orientation.
Finally, as has been shown, scientific studies strongly indicate that homosexual orientation is something people are born with. Available evidence favors mostly a genetic cause but some intrauterine effect before birth can not be excluded. As genetic research continues to advance, considerable light should be shed on the subject. A single gay gene is very unlikely to be found to explain a phenomenon as complex as human sexuality. Most likely the interaction of multiple genes will be involved.
Understanding the science behind homosexuality is no mere academic exercise but has practical consequences. Studies have shown that the public is more tolerant of gays and legislators are more likely to pass laws protecting their rights when the scientific facts are known.
with mankind, as he lieth with a woman, both of them have committed an abomination: they
shall surely be put to death; their blood shall be upon them.” It is not surprising that this sort
of pronouncement sometimes leads to intolerance and in extreme cases to assaults and even
murder.
In a study done at Kent State University on nursing students in 1999, researchers found
there was a significant correlation between homophobia, frequency of church attendance, and
Christian Orthodoxy.The Christian religion, especially the Catholic and the Fundamentalist
Protestant branches, has contended that homosexuality is a sinful life-style choice, one that is
voluntarily entered into, and one than can be abandoned if desired.
Unfortunately, I seldom hear individuals quoting scientific evidence but only biblical
references and long held prejudices. Even my fellow physicians are often unaware of the scientific
literature on this subject.
Sexual orientation refers to whether a person’s erotic desires are directed toward the
same sex (homosexuality), the opposite sex (heterosexuality), or both sexes (bisexuality). A
person’s actions may not always match his or her sexual orientation, such as when a person
conceals his sexual orientation for practical reasons. In this discussion we will be focused on
sexual orientation.
Seldom do we hear from psychiatrists and psychologists, who encounter homosexuals in
their practices, or from scientific researchers. In 1973, on the basis of research findings, the
American Psychiatric Association removed homosexuality as a disorder from their official manual,
the Diagnostic and Statistical Manual of Mental Disorders. Their conclusion was: “The reality is
that homosexuality is not an illness. It does not require treatment and is not changeable.” They
further added: “There is no published scientific evidence supporting the efficacy of ‘reparative
therapy’ as a treatment to change one’s sexual orientation.” In 1975, the American Psychological
Association passed a resolution supporting the conclusions of the American Psychiatric
Association. The World Health Organization passed a resolution in 1990 to remove homosexuality
as a mental illness from its official manual. In 2000, the American Psychiatric Association
reaffirmed its position of 1973 and stated that “in the last four decades, ‘reparative’ therapists
have not produced any rigorous scientific research to substantiate their claims of cure.” In 2001,
The United States Surgeon General, David Satcher M.D., issued a report maintaining that “there
is no valid scientific evidence that sexual orientation can be changed.”
In considering the cause of homosexuality, there are three possibilities: environmental,
intrauterine effects during pregnancy, or genetic.
First, let’s discuss the longstanding and firmly held belief that there is something different
in the environment that causes a person to be gay. Sigmund Freud, Alfred Kinsey, William
Masters, and Virginia Johnson held that homosexuality was socially learned. Bailey and Pillard,
however, researchers that have published the most studies in the field, reviewed all the scientific
evidence in 1991 in the Archives of General Psychiatry and concluded: “Previous attempts to test
psychodynamic and psychosocial theories have largely yielded negative findings and emphasize
the necessity of considering causal factors arising within the individual and not just his
psychosexual environment.” This very cautiously phrased scientific statement is basically saying
that these researchers reviewed all of the studies and the evidence for any environmental cause
of homosexuality is lacking.
Although intrauterine influences are suggested as a factor in homosexuality by a few
researchers, the limited amount of scientific evidence available is too fragmentary to determine if
it is significant or not. Most of the scientific findings strongly favor a genetic origin. At any rate,
sexual orientation is something that people are born with and is not acquired.
Evidence Supporting a Genetic Cause of Homosexuality:
Twin Studies.
Multiple twin studies have demonstrated a hereditary component to homosexuality.
Monozygotic twins (ones from a single ovum) share exactly the same genes, whereas dizygotic
twins (one from two different ova) share 50% of their genes, the same as any non-twin sibling).
The number of gays in the U.S. Population is 3-4% for males and 1-2% for females.
Since monozygotic (also called identical) twins share identical genes, the chance of a
match in sexual preference should be evident if heredity is operative. In the case of dizygotic (also
called fraternal) twins, since only half the genes is shared, a figure of about one half of that for
identical twins would be expected.
As examples, the results of two studies by Bailey and Pillard, are presented, but other
twin studies have yielded similar results. One study was limited to males where it was revealed
that if one identical twin was gay, the other was gay 52% of the time. If one fraternal twin was
gay,the remaining twin was gay 22% of the time. In the other twin study, which was limited to
females, if one identical twin was gay, the other one was also gay 48% of the time, and if one
fraternal twin was gay, the other was also 16% of the time.
Even though the observation that the approximately 50% concordance in homosexuality
in identical twins points to a strong heredity component, this figure could also suggest that
genetics might not be the entire explanation. But this 50% figure is still consistent with genetics
alone being the cause. Two examples of hereditary diseases in identical twins will show why.
If identical twins have the genes for Huntington’s Disease, both twins will develop the
disease 100% of the time. However, if identical twins have the genes for Type 1 Diabetes, both
will have only a 30% chance of developing the disorder. Therefore, even though identical twins
have identical genes, the manifesting of the genes can vary, a process called variable
penetrance, a phenomenon that is poorly understood at this time.
Animal Studies.
- Recent genetic studies on the geneticists’ favorite subject, the fruit fly (drosophila
melanogaster), has provided valuable information to scientists about homosexuality. The fruit fly
has a recognizable match with 75% of known human disease genes and has contributed valuable
genetic information to scientists for almost 100 years. Manipulation of a single gene
called “fruitless” induces homosexual behavior in either sex. Normally, a male fruit flies’ ritual for
the seduction of the female fruit is dramatic and involves such maneuvers as tapping her with his
foreleg, extending and vibrating his wings in song, and then brazenly licking her. This male sexual
behavior is exactly reproduced in females with the manipulation of the “fruitless” gene. In another
recent study on fruit flies, David Featherstone and coworkers discovered that a mutation in a gene
they call “genderblind” turns fruitflies bisexual.
- Studies on animal sexual behavior have been revealing. Homosexual behavior has now
been well documented in 500 animal species.
Anatomical and Physiological Differences in Gays.
These associated findings are further evidence that homosexuality is biological,
something that people are born with. I’ll just list the differences since the list is long:
- Gays are 39% more likely to be left-handed than straight people.
- Men typically have a ring finger that is longer than the index finger, while in women the
two are about the same length. Two studies have shown that in lesbians the ratios between the
two fingers are similar to those in men.
- One study compared fingerprints in men of the thumb and index fingers. 30% of
homosexuals had an excess of ridges on the left hand, whereas only 14% of heterosexuals did.
This finding is particularly interesting since fingerprints are fully determined in a fetus before the
17th week of pregnancy and do not change thereafter throughout life.
- The startle response (eye blink following a loud noise) is masculinized in lesbians and
bisexual women.)
- Gay and non-gay people emit different armpit odors.
- There are anatomical and physiological differences in the brain: The average size of the
INAH-3 (a part of the hypothalamus) in the brains of gay men is approximately the same size as
the significantly smaller one of women. The anterior commissure is larger in gay men than in non-
gay men. Three regions of the brain (medial prefrontal cortex, left hippocampus, and right
amygdala) are more active in gay men than non-gay men when exposed to sexually arousing
material. Gay and non-gay brains respond differently to two human sex pheromones (AND, found
in male armpit secretions, and EST, found in female urine).
Behavioral traits.
To varying degrees, gays often show characteristic behavior that appears to be a
biological part of their nature. Gay males tend to show variable degrees of feminine behavior and
lesbians variable degrees of masculine behavior, and these findings often are discernible in early
childhood. Of course, in some cases gay individuals show behavior that is indistinguishable from
heterosexuals.
Casual observers can often judge sexual orientation with very limited information. A 1999
Harvard study found that by simply looking at photographs of seated strangers that
undergraduates could identify the sexual orientation accurately 55% of the time. In another study,
112 undergraduate observers saw only the backsides of subjects as they walked on treadmills.
The observers correctly identified the sexual orientation of males with over 60% accuracy, but the
categorization of women did not exceed chance. As another example of readily available
behavioral clues to a person’s sexual orientation, a researcher, Gerulf Rieger shows videotapes of
men and women discussing the weather, and observers are able to tell who is gay and who is
straight with great accuracy. Rieger states that “even within seconds, people are pretty good at
figuring out who’s gay and who’s not.” Rieger thinks his research points to genetics as the source
of sexual orientation.
Finally, as has been shown, scientific studies strongly indicate that homosexual
orientation is something people are born with. Available evidence favors mostly a genetic cause
but some intrauterine effect before birth can not be excluded. As genetic research continues to
advance, considerable light should be shed on the subject. A single gay gene is very unlikely to
be found to explain a phenomenon as complex as human sexuality. Most likely the interaction of
multiple genes will be involved.
Understanding the science behind homosexuality is no mere academic exercise but has
practical consequences. Studies have shown that the public is more tolerant of gays and
legislators are more likely to pass laws protecting their rights when the scientific facts are known.
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