The principal flaw in Prof Sykes' argument in his article below is that the mitochondrial genes (which are passed from one generation to the other only via the mother) are nothing to do with any other function in the human body cell but to supply energy to all the other protein construction activities going on in the cell. All other genes that the original mitochondrial bacterium might have carried have long since atrophied or have moved to the host's DNA and are transmitted from there each generation via both the male and the female lines.
I believe that the rampant homosexuality of today is certainly driven genetically in the sense that 99% of homosexual activity is not social but purely to do with the sexual act. Homosexual couples in normal social or partnership situations are as rare as hen's teeth even though they now have complete legal permission to be so. It is just another sign -- like the enormous rise of singledom and the steep decline of family size -- of modern society under great stress. Homosexuality is a classic stress symptom in several species of social mammals besides ourselves. (The versatile sexual activity of the bonobo chimpanzee is not homosexuality at all but is just an extreme expression -- albeit exquisite no doubt -- of group-bonding. All such "gays" or "lesbians" that are observed produce offspring in the normal way.)
However, Professor Bryan Sykes, in his forthcoming book, "Adam's Curse" is determined to be mischievous in order to make his book a best-seller. In another preview article of his, which I have already copied here, he hypothesised that the male Y chromosome is degrading even though it doesn't need corresponding genes in the female X chromosome in order to self-repair after fertilisation because it contains palindromic genes which mostly self-repair in 'mirror-like' fashion. Both this hypothesis and the one below may turn out to be right, but in the scientific domain they are still exceedingly controversial and need a lot more investigation. They should not belong in a populist book, but he's taking advantage of a liberal society, just as homosexuals do. (It is interesting that Prof Sykes has not found an academic publisher for his book! Academic publishers are just as keen these days to publish populist books, as academic ones -- so long as they are responsible and balanced.)
KSH
<<<< WHY MOTHER DEAREST MIGHT PREFER HER LITTLE BOYS GAY
Homosexual men might be the result of a mother's selfish gene
Bryan Sykes
As a geneticist I have been curious about homosexuality for a long time. The curiosity is that if there is a genetic basis to homosexuality, then there must by definition be genes involved. The question is how do the genes get passed on from one generation to the next?
After all, at the simplest possible level, sex between partners of the same sex, while it may be fun, cannot result in children. I have worked on inherited diseases for a good part of my scientific career and there is no denying that homosexuality has some of the genetic characteristics that you might find in a serious inherited disease.
As I write I can hear the loud objections and imagine being accused of saying that homosexuality is abnormal. But the point of comparison to serious inherited diseases is that there are good explanations for why some of them are as common as they are, even though they hugely diminish the chances of the sufferer passing on his or her genes.
That is the comparison I am making because, when all is said and done, male homosexuals have fewer children than most heterosexual men. That is the puzzle. If there is a gay gene, why did it not become extinct long ago?
These are exactly the same questions we need to ask about a serious genetic disease. The fact that homosexuality is not a disease doesn't matter so long as it reduces the chances of the gene being passed on. If having brown eyes meant you didn't have children, nobody would have brown eyes toy longer.
In the early 1990s Dean Hamer and his colleagues from the National Institutes of Health in Washington DC took a look at the genetics of male homosexuality and in 1993 he claimed to have found a region of the X-chromosome on which a gene predisposing to male homosexuality was located.
Within hours of publication the news of the discovery of "the gay gene" was flashed round the world. From drawing out family trees of his gay male volunteers, Hamer noticed that a lot of the men also had gay uncles, but only on their mothers' side.
Hamer and his colleagues then tested the volunteers and their relatives to see whether or not in each family tree the gay men had all inherited the same X-chromosome, the rationale being that if they had, this was proof that a gay gene lay somewhere on that chromosome.
Many gay men who had felt either guilt or confusion about their sexual orientation took comfort from the news that it was a gene rather than themselves that was responsible for their homosexuality. Others complained that research into the biology of male homosexuality was basically unethical and should be banned. At the other extreme, homophobes declared that a "cure" for homosexuality through gene therapy was just round the comer.
Scientific outrage was confined to a technical attack on the statistics used by Hamer, and the publication was followed by a chorus of algebraic disapproval. Neil Risch, the author of one critique, decided to get his own data. Risch's large-scale survey, published in 1999, appeared to refute Hamer's claims.
So we are left hanging. One set of results says there is a predisposing gene for male homosexuality, another says there isn't.
I began to wonder if the genetic basis for male homosexuality might have nothing to do with the X-chromosome at all, or any other chromosome. I went back to Hamer's original paper. I could see easily how he had tracked the inheritance of male homosexuality through the gay men's mothers and why this pattern had drawn his attention to the X-chromosome. There were no instances of gay fathers with gay sons -- but that was hardly a surprise, since the gay men didn't have any children. The family trees only pointed a finger at the X-chromosome; they did not prove the gene lay there.
Could the same pedigrees, I wondered, be compatible with an inheritance influenced not by the X-chromosome, but by the "female" mitochondrial DNA? This DNA passes through eggs, not sperm, and while a mother gives her mDNA to all her children, only her daughters pass it on to the next generation. It is a selfish DNA, one which would prefer a female-only species. I wondered whether homosexuality could be an example of mDNA "disabling" men.
The answer leapt out. Mitochondrial DNA might be a symbol of femininity, but it still carries genes with the blind ambition of getting through to the next generation and beyond. The mother I can see out of the library window playing outside with her young son obviously loves him -- but her mDNA doesn't. Her mDNA wants her to concentrate on having daughters. Her mitochondria would do much better if she could eliminate all her male foetuses. And if this is not possible, she would see to it that it got no further. She would turn her son into a homosexual.
This hypothesis solves the major theoretical obstacle to the "gay gene" paradox -- the puzzle of how such a gene could survive and not be eliminated by its failure to be passed on through gay men. That vanished at once, because if the genetic element were associated with mDNA it wouldn't get passed on by men anyway. It is inherited maternally. Of course, not all mDNA can have refined this art or the world would be full of non-breeding men or, rather, we would already be extinct.
I looked back at Hamer's pedigrees and saw that it would work. A mitochondrial inheritance was just as possible as an X-chromosome association. A mother passes her mDNA onto all her children and, of course, there were plenty of examples of men whose brothers were gay but who were not gay themselves, even though they had the same mitochondrial DNA. But I didn't see that as a problem. I never imagined the mechanism for making a son gay was actually encoded by the mDNA itself. That just supplied the motivation.
Perhaps mothers whose sons became gay had just not managed to eliminate them while they were in the womb. There is a famous`example in the 1940s of a French woman from the city of Nancy who came from a family that has produced 78 daughters over nine generations and not a single son. Had these women's bodies found a way of refusing to have their eggs fertilised by sperm containing Y-chromosomes? Or had the mDNA subverted the implantation mechanism to reject all male embryos or arranged to abort all male foetuses? How many other wombs invite, only to destroy?
If this theory is true, there is no necessity to destroy gay sons, since they are unlikely to reproduce. If gay sons were the victims of failed attempted intrauterine elimination, did their mothers also have a record of successful prenatal homicide? I looked again at the family trees. Did the gay men have more sisters than brothers? Not particularly. In the families of the gay men there were roughly the same numbers of brothers and sisters.
But when I looked back a generation to see whether the mothers themselves had more brothers than sisters, there were far more girls than boys. I found out later this was generally true. In a survey of nearly 500 gay men, their mothers had a total of 209 sisters but only 132 brothers. Of course, they ought to have had roughly equal numbers of brothers and sisters. These gay men had far more aunts than uncles. So what happened to the missing 77 brothers? Had they been killed while in the womb? Had these mothers been even more successful at eliminating the male embryos and their Y-chromosomes than their daughters, who could only neutralise their sons by steering them towards homosexuality?
I am only too well aware that my theory is inadequate as a complete explanation for male homosexuality, and it isn't meant to be that. I am just happy that the headache that has dogged me for years about the virtual impossibility of an orthodox gene for male homosexuality surviving rapid extinction has now stopped throbbing. That the homosexual man and his Y-chromosome are casualties in the genetically embedded war between the sexes makes much more sense.
But are the motives purely those of revenge? Could a mother's mDNA actually have anything to gain from having a gay son? For some time I couldn't see what it could possibly be. Then, much later, I realised an answer lay in the beehive I observed in a museum. Could a gay son possibly be doing for his mother what sterile workers were doing for their queen bee?
Could a gay son be helping his mother to bring up his own sisters? That would be a direct benefit to the mother's mDNA. Any such small advantage would be very useful indeed and mDNAs with that ability would do very well, even if they had made all their sons sterile. That would elevate male homosexuality to a true piece of genetic altruism. It is a subtle plan by mDNA, not only to get rid of Y-chromosomes but to help itself at the same time.
Sunday Times 24 August 2003
"Adam's Curse" by Bryan Sykes is published by Bantam Press on September 4. >>>>
Keith Hudson, 6 Upper Camden Place, Bath, England, <www.evolutionary-economics.org>
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