The search for the gay gene
BMJ 2005; 330 doi: https://doi.org/10.1136/bmj.330.7498.1033 (Published 28 April 2005) Cite this as: BMJ 2005;330:1033
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I believe human sexuality to be far to complex to ever reach a
conclusive 'cause' for homosexuality. Maybe people should just accept its
just a matter of taste?
I also inherently believe that when studying such delicate topics,
religon should be firmly kept at arms length, as religon is just belief -
not fact. Relgious views should not be imposed on those who do not
believe and certainly should be not allowed to influence scientific
research - which unfortunately religon has done for far too long.
Lesbianism - is not an illness. As defined by the oxford medical
dictionary. Whereas it goes on to define homosexuality as a 'condition'.
It is amazing how these two defintions accept female homosexuality and
seem to reject male homosexuality.
I put it to the readers of this website that research along these
lines is just plainly silly and it is impossible to find anything
conclusive because any conclusions will just be skewed by societys
perceptions.
Male homosexuality is inherently disliked because we live in a male
dominated society and because of this male domination, lesbianism and the
exploitation of women are viewed as more desirable.
It would be interesting to see whether we would be having this same debate
if our society was controlled by females, I highly doubt it.
I think we would be too busy trying to find the 'cause' of lesbianism and
furthermore male homosexuality would be seen as a desirable quality.
One last point, heterosexuality and homosexuality are two minorities
at opposite ends of a scale. Bisexuality is actually more prevelant, how
can anyone explain that even on a combined genetic/enviromental basis?
It's merely impossible.
The geneticists will argue bisexuality is due to incomplete
penetrance of a multi locus gene.
The Freudians will argue that their father/mother was never there for
them.
I argue that this all should stop.
Competing interests:
None declared
Competing interests: No competing interests
A medical student believes that researching the supposed differences
between cognitive abilities of heterosexual and homosexual people is
pointless, inaccurate and ethically unacceptable as researching supposed
cognitive differences between different races. This is a pity.
I was interested in the results of tests in homosexual individuals
reported in the book, “Brain Sex” because of my experience in dyslexia.
The range of various tests used by clinical psychologists can be very
helpful and often give confidence to a dyslexic child who is worried that
he or she is “just stupid” when they fall behind in class. It is not my
experience that the tests used, for example by the Dyslexia Institute, are
inaccurate or pointless. Tailored remedial education can be started if
needed or appropriate career choices can be made, such as art or drama.
It would be important to know if maternal zinc and copper imbalance
in early pregnancy was involved in activating parental gay genes and in
altering brain orientation. Maternal zinc deficiency in early pregnancy
can impair a child’s stress responses and cause zinc deficiency in the
child and impair immunity, unless corrected by supplementation. This type
of research should not be regarded as ethically unacceptable but as useful
disease-preventing work. Many heterosexual and homosexual people are keen
to improve their immune systems today and welcome such scientific
research.
Competing interests:
None declared
Competing interests: No competing interests
Author's details removed at author's request on 4 June 2009.
Most doctors and researchers would agree that the broad aim of
medicine is to promote health and diminish disease. I therefore have
difficulty in understanding why a genetic cause for homosexuality is being
sought. Is it not surely unethical to spend time and money researching a
harmless part of life when that same time and money could be spent
researching an actual disease? I also believe that researching the
supposed differences between cognitive abilities of heterosexual and
homosexual people as pointless, inaccurate and ethically unacceptable as
researching supposed cognitive differences between different races.
I'm gay, and happen to believe that in my case this is genetic. My
partner, on the other hand, believes that he might be gay due to
environmental influences. We both might be right, but essentially neither
of us really care. The important thing is that we're both very happy, with
ourselves, each other, our work, and our lives in general. The only thing
that needs to be 'cured' or 'prevented' is the prejudice and
discrimination that still exists in a supposedly enlightened twenty first
century.
Competing interests:
None declared
Competing interests: No competing interests
Barry Savage's statement is logically flawed -
'If identical twins, separated at birth and raised independently, are
far more likely to be either both straight or both gay than any two people
picked at random, then this effect must be genetic, because there are no
other factors that could account for it'
Both twins shared the intra-uterine environment, and hence there ARE
other factors that could account for it.. such as maternal hormone
exposure, etc.
Can Barry give a reference for this research ? Was there discordance
between non-identical vs. identical twins ?
I feel sure that the causation of sexual orientation might be both
enormously complicated and very simple at the same time - but teasing out
specific genetic and environmental influences must add to our
understanding.
Competing interests:
None declared
Competing interests: No competing interests
Editor,
A balanced criticism of any research must weigh equally, both its
merits and demerits, and in weighing them, must be able to conclude if one
overweighs the other. I think Professor Murphy's article (1) failed in
this regard. I consider my arguments in consideration with, yet detached
from the professor's article.
Firstly, one must recognise that the ultimate goal of any research is
to understand the working mechanisms behind a complex trait. In that
sense, it is more important to know what complex mechanisms operate to
result in the genesis of homosexuality, genetic or otherwise. It would, I
believe, provide us with answers that would explain several questions
facing the study of sexuality as a whole. The overtly oppressed community
deserve some answers, and trust science to put it right. It is that
overwhelming duty that befalls scientists, than addressing whether or not
there might be political consequences.
Second, 'normal' is only defined within the constraints of human
perception, than within the strict realms of science. In that way, even
heterosexuality cannot be considered 'normal', for once there was no
sexual reproduction. Evolution split the sexes up only for better
efficiency of reproduction. Would it be too difficult to reckon that
homosexuality might be just one such aspect of evolution? What the critics
of homosexuality consider natural or normal cannot be truly defined within
the confines of science. Hence, a worry that this study tends to
'normalise' homosexuality is unjustified and unfounded.
Thirdly, human values and social perceptions of morality change from
time to time. And always, hard scientific facts help shape such
perceptions. Nobody believes anymore that the earth is flat, or that evil
spirits are responsible for human or animal disease. Similarly, only a
complete analysis of the genesis of sexuality will help address all
aspects of homosexuality, medical (should I remind the readers about the
ills of aversion therapy (2) published in this journal itself?) and
social. This means that the xenophobic attitude largely displayed to
homosexuality is wholly irrational, just in the same way that wholly
believing it to be genetic is.
Particulary worrying was the professor's drawing a comparison between
a clearly immoral trait (homicidal impulse) and a poorly misunderstood,
rather harmless trait. What two people of the same sex do within the
confines of their bedroom should be of no matter to others - it is a
matter of their own privacy. Can the author possibly clarify what the
society should find immoral with homosexuality, provided it is not
rampantly advertised, commercialised and propagated like heterosexuality?
With insights provided by nature itself (see above), does he believe
homosexuality to be any more unnatural than heterosexuality; whereby not
realising that man tampers with nature everyday when he utilises
contraceptives, that humanity is not just designed to reproduce, but have
some degree of divorce from their genes, if not to a greater degree?
It is perhaps best to study this complex sexual trait scientifically
and neutrally to the fullest possible extent; and then speculate on what
the ultimate social and political consequences might be. Hence, it is more
important to support this research, than criticising it with unfounded
'moral' worries. The ultimate aim of research should be aimed at
betterment of humanity, not just debunking or upholding a held principle.
REFERENCES
(1)Timothy F Murphy
The search for the gay gene
BMJ 2005; 330: 1033
(2) Twisselmann B. Treating homosexuality as a sickness. BMJ
2004;328: 956.
Competing interests:
None declared
Competing interests: No competing interests
In his personal view, Prof. Murphy lifts-up a very controversial
issue: the genetic origin of male homosexuality (1). After reading the
full article of Mustanski et al. (2) I think it is important to stress
what Mustanski et al. did not find. For the moment being, the data
presented in the aforementioned article is suggestive and far from being
conclusive to support the genetic origins of male same-sex
attraction/behaviour.
The authors acknowledge the limitations the study:
a) it was carried
out in a sample of “self-reported” gay males, hence lacking a control
group of “self-reported” heterosexual males
b) the small sample size
c)
particular software technical limitations
d) the study was not performed
in women (2).
Therefore, it would be desirable for the scientific
community and the concerned individuals, that this kind of studies were
performed in larger samples, with a different design including a control
group and applying uniform techniques for the sake of repeatability.
It is important also to highlight that the authors clearly state that
their findings cannot be extrapolated to the population, not even to males
that engage sexually with other males, and who do not identify themselves
as gay. Since the definition of homosexuality is complex, and previous
research found that some gay men can change their orientation following
specific therapies (3), care should be taken when generalising or
commenting on the findings of Mustanski et. al.
1. Timothy F Murphy. The search for the gay gene. BMJ 2005; 330: 1033
2. Mustanski BS, Dupree MG, Nievergelt CM, Bocklandt S, Schork NJ,
Hamer DH. A genomewide scan of male sexual orientation. Human Genetics
2005;116: 272-8
3. Spitzer RL. Can some gay men and lesbians change their sexual
orientation? 200 participants reporting a change from homosexual to
heterosexual orientation. Arch Sex Behav. 2003 Oct;32(5):403-17
Competing interests:
APC is Evangelical Christian
Competing interests: No competing interests
If identical twins, separated at birth and raised independently, are
far more likely to be either both straight or both gay than any two people
picked at random, then this effect must be genetic, because there are no
other factors that could account for it; so if you accept these data there
is no argument about whether there is a gay gene: there is.
However, it's also true that there are plenty of exceptions: one
twin can be gay and the other straight. Genes can be turned on by
experiences or by other genes. So there is still the question, "What
turned the gay twin's gay gene on?"
Gay people will say, "I was born this way", but even if there is a
gay gene, the data doesn't support that argument. It isn't inevitable that
the bearer of the gay gene will adopt a gay lifestyle. That depends on
the effect of other genes, penetration and experiences.
Competing interests:
None declared
Competing interests: No competing interests
It is interesting that Hamer and colleagues previously found a
linkage between DNA markers on the X chromosome and male sexual
orientation.1 Now they also report approximately equivalent maternal and
paternal contributions at a position near D7S798 in 7q36 (mlod score 3.45)
and also near D8S505 in 8p12.2 (mlod score 1.96).2
Dr Gibbon refers to Moir and Jessel’s book “Brain Sex” noting that an
excess of male homosexual children can arise as a result of influences
during pregnancy such as hormone therapy or severe fright.
Besides distorting hormone levels in a developing foetus, maternal
hormone therapy can cause zinc deficiency, as does fright or famine. Zinc
is not only essential for normal brain development and function but it
also needed for normal testosterone production at the critical times of
brain sexual development. Homosexuality and dyslexia are more common in
males than in females, perhaps because males have a greater need for zinc.
Homosexuality and dyslexia seem to have both genetic and
developmental components in early pregnancy. Gene expression can be
altered with different balances of zinc and copper. Maternal zinc
deficiency may prevent the development of the usual degrees of cerebral
dominance in either right or left hemispheres causing cross laterality. In
tests of special ability homosexual men scored lower than heterosexual men
but higher in tests of verbal fluency. Their cognitive abilities were
intermediate between those of heterosexual men and women.3
I do not understand why women with unexplained infertility are given
sex hormones and gonadotrophins. Exogenous hormones can increase zinc and
copper imbalances which too often remain undiagnosed and uncorrected
before conception.
1 Hamer DH, Hu S, Magnuson N, Pattatici AML. A linkage between DNA
markers on the X chromosome and male sexual orientation Science
1993:26:321-27.
2 Mustanski BS, Dupree MG, Nievergelt CM, et al. A genomewide scan of
male sexual orientation. Hum Genet. 2005;116 :272-8.
3 McCormick CM, Witelsan SF. A cognitive profile of homosexual men
compared to heterosexual men and women. Psychoneuroendocrinology
1991;16:459-73.
Competing interests:
None declared
Competing interests: No competing interests
I was surprised to read Prof. Timothy F. Murphy's review of a paper
in "Human Genetics" by Dean Hamer. Prof.Murphy suggests that there is a
"growing sense that genes play a role in male sexual orientation" though
no figures are given by either author.
I have always thought it to be axiomatic that homosexuality cannot be
inherited apart perhaps from some borderline cases. Certainly, the
condition is congenital and so far irreversible but this could be
determined by the mother's sexual hormone status during her pregnancy.(See
"Brain Sex" by Ann Moir and David Jessel, Delta Dell Pubs.)An excess of
male homosexual children can arise as a result of influences during
pregnancy such as hormone therapy or severe fright ( e.g.during air
raids.) Before the public can be expected to decide what attitude to adopt
towards homosexuals it is essential that the underlying causes be fully
revealed.
Competing interests:
None declared
Competing interests: No competing interests
Where is the search for a Christian gene?
Certainly Christianity is far more heritable than homosexuality.
Why look for either a genetic or an environmental "cause" of
homosexuality? From my perspective, it is a happy accident that I turned
out gay in response to the society in which I live. Had I lived in another
society with far different conceptions of the role of human sexuality, who
knows what I would have become?
Competing interests:
None declared
Competing interests: No competing interests