Evolution and female orgasm

Any smirks should be wiped off faces, for this is an academic post on a subject of several recent Kuhnian revolutions. Since female orgasm is not necessary for conception (ask any Pramface lassie), its nature, function and modus operandi are particularly interesting.

The historical/philosophical background of female orgasm is one first of absenteeism, then of Freudian good/bad vaginal/clitoral forms, then mid 20th C physiological studies proving its clitoral origin (Kinsey) and surveys showing only a third acheive orgasm through penetrative sex alone (Hite). Referral patterns to sex therapists show an overwhelming gender bias of premature ejaculation in men and anorgasmia in women. Conversely, anorgasmia in men is almost always physiological in origin (physiological impotnece or foreskin insuficiency) and premature orgasm in women is vanishingly rare.

The evidence is overwhelming that reproductive sexual behaviour (penetrative sex) is more likely to lead to climax for men then women. Nevertheless, even anorgasmic women enjoy sex, and orgasmic sexuality, relationships and family life remain a preoccupation for women at least as much as men. And it's this that drives much of the advertisement industry, and the enormously profitable porn industry.

However my interest is neither personal (since I know how to get there) nor political (since to me the sex industry is a fact). But evolutionary theory can help to examine and analyse female orgasm's significance by examining the evidence.

Three suppositions I discounted are these:
1. That the evolution of female orgasm has yet to catch up with the mechanisms of penetrative sex, and that in time the clitoris will move southward closer to the vagina.
2. That the uterine contractions of the female orgasm function adaptively to wash sperm upstream to fertilise a waiting ovum.
3. That the human clitoris is adapted for face-to-face sex, as frequently practised by humans.

1 a) Sexual reproduction evolved a very long time ago in single cells, and has continued to have been employed in most eukaryotic, multicelled organisms. That evolution has been 'too busy' to move the clitoris south in humans is not rational.
b) Female fertility peaks at approx ~20 yrs, while orgasmic capacity for women increases with decline in fertility from 35 yrs onwards.
c) Women can have orgasms at all times of their cycle, whether fertile that day or not
2 a) Female orgasm is not needed for conception
b) Women have variations in their orgasmic capacity over their ovulatory cycle. While some peak in libido and orgasmic capacity at ovulation in most women peak sexiness corresponds with their least fertile periods (just before menstruation).
3 If the clitoris is placed to produce simulataneous orgasm in both human sexual partners, why isn't it located in the vagina or the throat (as fantasised in a famous film).
In the Mating Mind, a book about sexual selection pressure's effects in evolution, Geoffrey Miller suggests that the elusiveness of the human female orgasm is an engineered mechanism for females to assess male's fitness as partners and parents. The normal strategy of male sexual organsims with a plethora of sperm is to inseminate as many females as possible, with a blunderbuss approach to reproduction. However, female reproductive strategy, with scarce ova, is to pick and choose the fittest male mate possible. In crabs, this might be the oldest, biggest male with the optimally adapted sperm, but in an altricial species with pair-bonding and optimally shared care of offspring the balance will shift.

It takes considerable care, expertise and patience to produce a female orgasm, most usually through direct clitoral stimulation. Miller's hypothesis that female orgasm is a tool for women's sexual selection of mates appeals to me very strongly, especially in the peculiar circumstance of human concealed ovulation. The remarkably long neoteny and extended care required by human babies quite rightly invokes special screening techniques for women, biologically, and a male attentive enough to produce an orgasm just could be an indicator of committment needed to get a baby past toddlerhood.

I came across this weekend a book on the subject- The Case of the Female Orgasm : Bias in the Science of Evolution http://www.amazon.com/exec/obidos/tg/detail/-/0674017064/102-5507064-2921703?v=glance but it was only available in hardback, and my shoplifting skills are rusty these days. It's probably developed better arguments than my amateur ones above, I'd hope, but until it's in paperback I'll remain ignorant.

PS My natural scientific/evolutionary bent means that I wish knowledge of the sexual behaviour and response in other animals besides humans, but I don't except for the wierd stuff, like the spotted hyenas who have clitorises as large as their males' penis, and who give birth through a shared urethral/vaginal canal in their clitoris. I'm particularly interested in the genital anatomy of primates, wondering how coitus with the male behind the female could access or stimulate a frontal clitoris. I believe the evolutionary blogger Pharyngula may have addresses some of these issues.