Homosexual genes and memes.

From: Keith Henson (hkhenson@rogers.com)
Date: Tue 01 Mar 2005 - 14:22:00 GMT

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    At 10:42 AM 01/03/05 +0000, Peter Baker wrote:

    >In message <200502281850.SAA24389@localhost.localdomain>,
    >fmb-majordomo@mmu.ac.uk writes
    >>But the animal should always prefer an opposite sex partner unless the
    >>homosexual behavior has some adaptive function other than breeding. This
    >>function may be to practice sexual skills without being pregnant, or it
    >>may be to form alliances, or whatever.
    >Obviously if the most frequent function of sex were procreation, then one
    >would expect a partner of the opposite sex to be strongly selected for...
    >But is it the most frequent use of sex?
    >Given our own personal experience of the matter it is so strange that
    >people still have this biblical view that sex is 99% for procreation, and
    >1% for sin, or other marginal reasons. Look at it this way... How many
    >times does the average human have sex in a lifetime? At a very rough
    >guess, once a week for 50 years? Say 2500 times in all? And how many
    >children on average? 2.5? So procreation accounts for about 0.1% of human
    >sexual activity. What the hell were we doing it for all the rest of the
    >time? And if it wasn't for procreation, then does it matter whether it is
    >with a partner of the same or different sex?

    As any parent knows, sex is a small part of reproductive success in humans. Kids actually need a tribe around them, but that starts with *two* parents who have to stay bonded for over a decade. Pair bonding borrows the same chemical, oxytocin, that mammals have used for over 100 million years to get mothers to take care of young. Both males and females humans release oxytocin at orgasm. I don't know of a study, but I would bet you
    *long* odds that a study would find pair stability directly related to oxytocin (and possibly vasopressin) peaks after sex.

    >Only if there is an adaptive benefit... and what Bagemihl shows (ignoring
    >the shortcomings you mention) is that evolution favours diversity on this
    >issue. Many, if not all mammals - including us - have the potential for
    >bisexual activity and relationships, and we swing one way or the other as
    >the situation requires. As humans, our MEMETIC makeup may predispose us to
    >deny it (and as an aside there is good scientific evidence that closet
    >bisexuals are the most vociferous in promoting anti-gay memes) - but that
    >doesn't change the fact that we are all bisexual.

    I am not into group selection driving genetic evolution for reasons that it just does not work out logically (the feedback path does not close). But in more violent times, groups that had memes for high reproduction may have done better in times of high death rates than groups that did not. You can make a modern case for it with Mormons and Catholics and an extreme counter example with the Shakers. Thus anti-gay memes would go in the same bin as anti-abortion, anti-infanticide and anti-birth control memes if you want a lot of effort put into raising more kids to become meme hosts. This loop
    *does* close.

    >I think my point here is to challenge the assumption that we need to
    >explain homosexual behaviour MORE than we need to explain other
    >non-procreative sex.

    Good point. And there is interesting early research indicating that male attraction to other males is due to genes that normally function to make women attracted to men.


    Survival of genetic homosexual traits explained 00:01 13 October 2004 NewScientist.com news service Andy Coghlan

    Italian geneticists may have explained how genes apparently linked to male homosexuality survive, despite gay men seldom having children. Their findings also undermine the theory of a single "gay gene".

    The researchers discovered that women tend to have more children when they inherit the same - as yet unidentified - genetic factors linked to homosexuality in men. This fertility boost more than compensates for the lack of offspring fathered by gay men, and keeps the "gay" genetic factors in circulation.

    The findings represent the best explanation yet for the Darwinian paradox presented by homosexuality: it is a genetic dead-end, yet the trait persists generation after generation.

    "We have finally solved this paradox," says Andrea Camperio-Ciani of the University of Padua. "The same factor that influences sexual orientation in males promotes higher fecundity in females."

    Relative differences

    Camperio-Ciani's team questioned 98 gay and 100 straight men about their closest relatives - 4600 people in total. They found that female relatives of gay men had more children on average than the female relatives of straight men. But the effect was only seen on their mother's side of the family.

    Mothers of gay men produced an average of 2.7 babies compared with 2.3 born to mothers of straight men. And maternal aunts of gay men had 2.0 babies compared with 1.5 born to the maternal aunts of straight men.

    "This is a novel finding," says Simon LeVay, a neuroscientist and commentator on sexuality at Stanford University in California. "We think of it as genes for 'male homosexuality', but it might really be genes for sexual attraction to men. These could predispose men towards homosexuality and women towards 'hyper-heterosexuality', causing women to have more sex with men and thus have more offspring."


    I don't think this is stated right since as Peter points out so few sex acts result in reproduction. But if these genes on average cause women to start earlier or continue having kids later, *that* would account for the higher reproduction.

    Keith Henson

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