[Paleopsych] NS: Genes blamed for fickle female orgasm

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Genes blamed for fickle female orgasm
http://www.newscientist.com/article.ns?id=mg18625033.900&print=true

      * 11 June 2005
      * Rowan Hooper

    IS THIS the ultimate excuse for poor performance in bed? "Sorry,
    darling," the man says, just before falling asleep. "It's your genes."

    According to a study published this week, up to 45 per cent of the
    differences between women in their ability to reach orgasm can be
    explained by their genes. Despite decades of surveys and conjecture
    about the role of culture, upbringing and biology in female sexual
    function, from Freud in 1905 to the Hite report in 1976, this is the
    first study of the role of a woman's genes.

    Its findings suggest there is an underlying biological basis to a
    woman's ability to achieve orgasm. Whether that basis is anatomical,
    physiological or psychological remains uncertain, says Tim Spector of
    the twin research unit at St Thomas' Hospital in London, who carried
    out the study. "But it is saying that it is not purely cultural, or
    due to peer pressure, or to differences in upbringing or religion," he
    says. "There are wide differences between women and a lot of these
    differences are due to genes."

    Spector's team asked more than 6000 female twins to fill out a
    confidential questionnaire about how often they achieved orgasm during
    intercourse and masturbation. They received 4037 complete replies,
    which included answers from 683 pairs of non-identical twins and 714
    pairs of identical twins. The women's ages ranged from 19 to 83, and
    about 3 per cent were lesbian or bisexual.

    Only 14 per cent of the women reported always experiencing orgasm
    during intercourse. Another 32 per cent of the women reported that
    they were unable to achieve orgasm more than a quarter of the time,
    while 16 per cent never achieved it at all. Comparing the results from
    identical and non-identical twins suggests that 34 per cent of this
    variation in ability to orgasm during intercourse is genetic.

    The idea behind twin studies is that pairs of twins grow up in similar
    environments. So if identical twins are more similar in some way than
    non-identical twins, then that similarity must be down to their
    identical genes rather than the environment.

    Unsurprisingly, more women were able to achieve orgasm through
    masturbation, with 34 per cent saying they could always do so.
    However, the figure for those who could never achieve it was only
    slightly lower, at 14 per cent. The analysis suggests that 45 per cent
    of this variation is genetic (Biology Letters, DOI:
    10.1098/rsbl.2005.0308).

    Spector says he was surprised by the similarity in the numbers of
    women unable to experience orgasm either through intercourse or
    masturbation. "With masturbation there are fewer external factors -
    i.e. men," he says. "So the higher heritability value for masturbation
    gives us a clearer picture of what's going on."

    The discovery of a genetic basis for the ability of women to orgasm
    raises questions about its evolution. One theory is that it is a tool
    for mate selection, the idea being that males best able to bring
    females to orgasm are also the best males to help raise children.
    Another is that the female orgasm produces movements that increase
    sperm uptake, and therefore fertility.

    But studies of other primates suggest otherwise. Female stump-tailed
    macaques have orgasms too - but mainly during female-female mountings,
    which hardly supports the fertility or mate-selection idea.

    Bonobos engage in highly promiscuous sex and mutual masturbation,
    complete with orgasms, a practice that is thought to promote group
    cohesion. This supports yet another theory: that orgasm is important
    in bonding.

    But even if orgasm does play this role, it cannot be crucial in
    humans. The finding that many women cannot achieve orgasm because they
    do not have the genes for it shows that the ability to orgasm is not a
    trait for which there has been strong evolutionary selection, says
    Elisabeth Lloyd of Indiana University in Bloomington, author of The
    Case of the Female Orgasm. This supports her theory that as far as
    orgasms are concerned, women have been riding on the genetic
    coat-tails of male evolution, and that the female orgasm is merely an
    accidental echo of the male one, the equivalent of male nipples.

    Lloyd says the findings also challenge the notion that the failure to
    achieve orgasm represents "female sexual dysfunction", an idea popular
    with companies keen to sell to remedies for this so-called disorder.
    "What definition of 'normal' could possibly justify labelling a third
    of women as 'abnormal'?" she asks.

    Even if struggling to achieve orgasm is nothing unusual, Spector says
    it might be possible to find ways to make it easier. Though hundreds
    of genes could be involved, "that doesn't mean we couldn't find the
    genes and pathways, if this was taken more seriously as a problem", he
    says.