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Health

Gay sheep, forbidden science?

Gene ExpressionBy Razib KhanJanuary 2, 2007 2:33 AM

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Science told: hands off gay sheep:

Scientists are conducting experiments to change the sexuality of "gay" sheep in a programme that critics fear could pave the way for breeding out homosexuality in humans.

You can read the whole article yourself. Randall Parker has been saying for years that genetic engineering will accentuate human differences as parents will choose to invest in alternative enhancements with their finite dollars. The vectors may remain the same, but the magnitudes could increase, as religious parents breed super-religious offspring, secular parents start spawning born atheists, and what not. There is a pretty obvious and straightforward way for homosexuals to calm down their fears that straight parents will genetically engineer out their orientation (ergo, community): breed gay babies. If scientists can understand homosexuality well enough to "cure" it, then they could certainly turn fetuses gay. Update: Just to be clear, just because

obligate homosexuality is likely of biological origin does not necessarily mean that it is genetically specified

. The evolutionary reasoning is pretty simple, obligate homosexuality is a reproductive fitness killer. There is a hypothesis that "gay uncles" may enhance the fitness of their siblings, but while the coefficient of relatedness between a parent and child is 1/2, that between uncle and niece or nephew is 1/4.^1 In other words the increase in fitness to the siblings has to be enormous in an inclusive fitness context. Another model for the biological origin of homosexuality is something like Toxoplasma gondii, a pathogenic infection which has a behavorial impact. Susceptibility to this putative pathogen might be genetically correlated, in other words some families might be more likely to be infected and exhibit "symptoms" than others. This story is less about genetics really than possible physiological re-wiring, which might have some psychological consequences. This also highlights the fact that lot of the "re-working" of our species biological substrate might not have a big germline impact. I alluded to this when discussing the low fitness (sterility for males) of Down Syndrome individuals. But be able to re-work psychology and physiology "on the fly" based on personal and social preference will obviously have a big impact if it becomes common. 1 - There is an idea that homosexuality is a byproduct of another genetically controlled trait which has been under selection. In other words homosexuality is a correlated response in a population due to pleiotropy at a locus. But this falls under the same problem that the inclusive fitess hypothesis does: selection would operate against a locus which resulted in a predisposition toward non-reproductive behavior as the primary sexual outlet. If it is pleiotropy than it is likely a recent genetically controlled trait since it seems likely that modifier genes would have masked fitness reducing byproducts in short order. I also think that it if is pleiotropy that Quantitative Trait Loci studies would have picked it up by now because it has to be a gene of massive selective power and ergo large effect.

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