SEXUALITY AND SCIENCE

Alan Sheard

The Church of England report ‘Some Issues in Human Sexuality’ published in 2003 claims that ‘The jury is still out on the causes of homosexuality’. This implies that little is known about homosexuality, but there is a great deal of scientific evidence about it that the Some Issues report completely ignores. Scientific research on this goes back to the 1950s, and indicates that a person’s sexual orientation is fixed, and in the great majority of cases is unalterable. This led to the removal of homosexuality from the list of recognised medical disorders in 1973. Further advances have been made in the past 25 years which confirm the position. In the late 1980s the Government sponsored, and the Wellcome Foundation funded, a very comprehensive survey of sexual attitudes in Britain, which revealed a great deal of information for the first time, and this was published as a book by Penguin in 1994. The sample was large enough to include statistically significant numbers in subgroups within the population. Then in 1991 Simon Leroy conducted a series of autopsies on homosexual men and showed that the anatomical structure of part of the brain was different in homosexual people. Much work has also been done on other lines of enquiry, which has led to the conclusion that sexual orientation is largely fixed by the time of birth.

Prevalence studies have shown that exclusively heterosexual or homosexual people make up almost all of the population, and bisexuality is rare. This is unlike most biological variables, such as adult height or blood pressure, where most people have values near to the average. This in itself suggests that sexual orientation develops on two different paths.

Historically, Sigmund Freud’s view of sexuality was accepted in the early 20th century that good mental health, and a heterosexual orientation, were dependent on a good relationship with the parents during the early years of life. Well constructed surveys to test this were not done until the 1960s, when it was found that neither homosexual people nor mentally ill people were more likely to have had a poor relationship with their parents.

The possibility remained that association with gay or lesbian people could lead to initiation of a young person into lifelong homosexuality. Again, detailed studies, particularly the one published by Penguin, have shown that this does not happen; the study shows that young people at same sex boarding schools do as a group show a higher proportion having homosexual activity, but, in a group who had left a same sex boarding school five years or more previously, the proportion still having same sex activity was no higher than in the general population. Also, in one of the tribes in New Guinea, children are made to have same sex relationships with adults, but the homosexuality rate in their adults is no higher than elsewhere. This is further evidence that homosexuality is not addictive, and not permanently altered by external influences. However the Church of England Report ‘Some Issues in Human Sexuality’ wrongly infers, in paragraph 4.4.64, that changes in sexual behaviour in some circumstances are evidence against an innate sexual orientation.

Enquiries into families have confirmed that homosexuality does cluster in families in a way that suggests it is inherited genetically. Identical twins have exactly the same genetic inheritance, and non- identical twins have half the same genetic inheritance. Studies have
been done of groups of twin pairs, in all of which at least one of every pair was homosexual. The second twin was also found to be homosexual in half of the identical twin pairs, and in 16% of non-identical twin pairs, and 6% of adoptive pairs. The finding that half of the second identical twins were homosexual indicates a strong hereditary influence, but also that there is another, non-hereditary factor also operating among those twins who were homosexual. Nevertheless, conservative Christian spokesmen claim that the lack of full concordance in the identical twin studies shows that homosexuality is not inherited.

Heredity therefore appears to be responsible for a predisposition to homosexuality, which must be triggered by some other influence. We have already noted the possible postnatal influences that might be responsible for this, which could be early parental effects or copied behaviour in later childhood, and found that these are not implicated in causing homosexuality to develop. But is homosexuality just a free will decision made by people, who are responsible for their own sexuality? There is a lot of evidence against this. Many homosexual people, often in response to the criticisms coming from religious organisations or individuals, have undertaken courses of ‘treatment’, often at great expense, to make them heterosexual. These almost always fail. A recent study by Professor Spitzer of New York University is frequently quoted by conservative Christians as showing that sexual orientation can change. He asked for people who had undergone therapy for homosexuality to contact him. Only 200 people responded, almost all of whom had had therapy because of religious criticism. He concluded that only 13 out of the 200 had become mainly heterosexual, and confirmed that for the great majority change of orientation is not possible. Conservative Christian commentators seem unable to understand that people differ, and cannot all be forced into the same pattern in this respect.

We therefore have to consider the one remaining possibility, that the environmental factor causing sexual orientation operates before birth, in the uterine environment. Sexual development in the foetus does not begin until the sixth month of pregnancy, when the baby is complete in almost all other respects. At that time the sexual organs develop and grow in the pelvis, and there is also a rapid change in the part of the brain known as the hypothalamus. Experiments on animals have established that the hypothalamus includes the nerve centre for sexual awareness and activity. This is one of the reflex centres in the brain that control different aspects of body functions, such as body temperature, the fight or flight response to danger, and body balance. The variability in voluntary control of a person over their reflexes is notable – there is none in the case of body temperature. When the hypothalamus is surgically altered in an experimental animal, the animal’s subsequent sexual behaviour becomes dramatically different. And biochemical tests have shown that the hypothalamus is specifically receptive to the sex hormones, oestrogen or testosterone, and their derivatives. Any prenatal influences on sexual orientation must be operating at this point, anatomically and in time.

By a process of trawling, ie designing and testing all conceivable hypotheses, which is the basis of the scientific method, it has surprisingly been found that males who have two or more older brothers have a small but significant increase in likelihood that they will be homosexual. A possible explanation is that a male foetus inside the mother’s body is essentially foreign to the mother, since she herself has no male tissues. As with other external substances entering the body, such as microbes, the mother’s immune system develops antibodies against them – in this case, against the male hormones in the developing foetus. Antibody formation is always a slow process, building up over several exposures, which in this case is over several male pregnancies. It is feasible to suggest that an antibody to the testosterone (or its derivatives) in the male foetus could alter the development of the hypothalamus at the critical sixth month stage of pregnancy, configuring the sexual reflex centre to recognise males rather than females as attractive.

This occurs in only a small proportion of male births, but similar hormonal variations in the developing brain could be occurring in other pregnant women, with female or male foetuses, and could account for other instances of homosexuality. There is a close analogy with Rhesus disease of the newborn, which is due to a reaction by a Rhesus negative mother to her Rhesus positive foetus.

The importance of the sex hormones in prenatal development is revealed by two rare medical disorders. One is Androgen Insensitivity Syndrome, in which a genetically male foetus is totally insensitive to the effects of the testosterone circulating in its body. These people grow up as women, and usually marry, but of course they are infertile. The other is Congenital Adrenal Hyperplasia, in which the child is genetically female, but has a tumour of the adrenal gland which produces the male hormone testosterone. If the tumour is removed surgically very early in life they grow up as heterosexual women. If it is not removed, as was always the case until recently, they grow up either as men, or as women
with a high probability of being lesbian.

Finally, it needs to be stressed that most homosexual people have no abnormalities. Every
person in the world is unique, with their own combination of characteristics, including such things as resting blood pressure, pulse rate, height, haemoglobin concentration et cetera. In a male foetus, a normal but low testosterone level during later pregnancy when the brain is developing may lead to a homosexual orientation, and in a female foetus a normal but high testosterone level may lead to a lesbian person, in the normal course of affairs.

This is a very brief summary of the main findings of the biological research into sexuality. A useful recent book is Born Gay by Wilson and Rahman, two London University Psychologists, published in 2005 by Peter Owen Books, which gives a fuller account. Also of interest is the British Medical Journal of 21 February 2004 on the history of the treatment of homosexuality up to the 1950s, pages 427 to 432, headlined ‘Treating homosexuality as a sickness, one of medicine’s many mistakes’; copies should be obtainable through libraries.

Some conservative Christian organisations have circulated reports of population studies which they claim show that homosexual people characteristically abuse children, are prone to drug taking, and are likely to die young. Their evidence is totally unreliable, being based on selective and unrepresentative population samples, such as convicted people or deaths mentioned in gay magazines, in which deaths of older people would hardly be newsworthy.

In the medical profession the debate is long past. Doctors are forbidden by the General Medical Council to allow their views on sexuality to affect the treatment they give or arrange for their patients. Surely it is time for people to receive the same understanding and acceptance by the Church.

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