First, yes, I am speculating too on this. Anybody who discusses this is speculating.
Inference from ethnography is that earliest families were not divided into monogamous units. Roughly speaking, all women of a generation were "mothers"; all men of a generation mothers' brothers to children. So, the "two parent" dynamic is probably not involved.
The obvious, most direct basis of selection for females with orgasmic capability is that they would want to have sex more because it feels good ( or can feel good). More sex had, more fertile sex likely to be had.
Fertile sex is _the_ main prize that Darwinian selection has its eye on. Fitness , in the Darwinian sense , is most directly correlated with "having fertile sex". Thus, if capability of having an orgasm causes having more sex, and having more sex causes having more fertile sex, then capability of having orgasms is selected for. ( This would be true for males too).
The criticality of _fertile_ sex to fitness, might mean selection for heterosexual inclination. Sex with just anybody would not be selected for , because fertile sex is what is selected for. Nothing about monogamy increases likelihood of fertile sex. Perhaps even the opposite , as Justin alluded to.
By the way, this doesn't contradict Gould's discussion of "spandrels" . Gould doesn't maintain that every human trait is like a "spandrel". Gould still holds that _some_ traits _are_ the result of direct selection. So, the point here would be that female orgasm is not a "spandrel-like" trait. It is a trait that is selected for. I would maintain that of all traits, those directly related to fertility are the most likely to involve actual selection.
What I mean by "the main prize in Darwinian selection" is that differential fertility is more important than differential mortality ,even. This is a conclusion of modern biology modifying Darwin's original focus on "struggle for existence." Reproduction is more directly important than "production" or "struggle for existence" in terms of "predator/prey" struggles. To put it vulgarly, "fucking ability is more important than fighting ability in measuring Darwinian fitness."
Mine is speculation too, a just so story.
CB
Miles Jackson
On Sun, 29 May 2005, Bill Bartlett wrote:
> Hardy doesn't seem to have the slightest grasp of how evolution works. The
> "Darwinian logic behind the female orgasm" is hardly "elusive", it seems
> fairly obvious to me that it might support the bond between parents over
the
> extended period necessary for humans to rear their children. The
"Darwinian
> logic" is that children being supported by two parents generally have an
> advantage over children supported only by one parent and sex seems to help
to
> keep mother and father on the team. I would have thought it unnecessary to
> spell out that an ongoing sex life is more likely if both parents are
> enjoying it.
Cue Justin; more "just so" stories! I can't resist engaging in speculation, though: Bill's argument doesn't even seem to work as a "just so" adaptation story. If a woman can have an orgasm with any sexual partner, male, female or herself (remember that intercourse is definitely not necessary!), why on earth would she be compelled to form a pair bond with just one man? You could just as plausibly argue that orgasm would encourage a variety of sexual relationships (but of course, that doesn't fit the "women are monogamous" stereotype, so we don't tend to make up "just so" stories about women's natural promiscuity).
Miles