On Thu, 9 Jun 2005, Charles Brown wrote:
> How exactly do you suppose increased masturbation increases fitness ? That's
> what a spandrel-like trait would be. Something that in itself has no
> adaptive value, but which is a side effect of something that is adaptive.
> Orgasm in masturbation is the better candidate for spandrel-like quality
> than the orgasm during intercourse, because increased intercourse increases
> fertility and increased masturbation does not do so as directly.
You're not getting the completely arbitrary linkages that are possible on the human genome. Spandrels are not just "side effects" that can be easily and clearly be linked to adaptive traits; they can be functionally distinct and completely unrelated. And again, you're ignoring the data: female orgasm is far more likely without intercourse than with it!
> Again the main point is that anything that directly increases heterosexual
> intercourse is extraordinarily likely to increase fitness via differential
> fertility, more likely than all other traits, all of which basically
> increase fitness by _in_directly increasing fertility.
I would agree with this completely if in fact heterosexual intercourse was a very common way for women to have orgasms. Given the fact that study after study has demonstrated that it is not, I'm compelled to disagree with you.
> Isn't masturbation a spandrel-like trait with respect to fertilizing
> function of the penis ? What do you want to bet that men have orgasms a
> higher percentage of the time masturbating than in intercourse ? Would you
> say the ability to have penis-orgasm in intercourse is a spandrel-like trait
> in relation to penis-masturbation? No.
What's sauce for the goose here isn't sauce for the gander. False analogy.
> My thought in response was why wouldn't both the clitoris and the penis be
> selected for ? Or ,afterall, since the original, fetal organ that both
> males and females have is the clitoris, not the penis, why not speculate
> that the penis is spandrel-like trait to the clitoris, which was the trait
> naturally selected for ?
Once more, if this were so, most women would easily achieve orgasm during intercourse, as men do. Given the data, your sociobiological just-so story is dubious.
> Why bend over backwards to look for a way to find that the clitoris and
> vaginal orgasm are not adaptive traits ?
Why bend over backwards--ignoring the relevant data!--to assume that they must be adaptive? The real lesson of Darwin, as I mentioned in a recent post, is not that all traits in a species are products of natural selection; it is that many traits persist and change in a species for reasons that have nothing to do with evolution!
Miles