Female Orgasm – An Evolutionary Mystery (Scientific American article)

note scientists would understand a lot more about orgasm if they studied it as a universal (yin-yang) principle….- M.

REOPENING THE CASE OF THE FEMALE ORGASM
By Jesse Bering
Scientific American
December 1, 2009

http://www.scientificamerican.com/article.cfm?id=reopening-the-case-of-the-f
emale-or-2009-12-01

Now that I’ve written at some length about the curious evolution of the male
reproductive system in our species <http://bit.ly/746TWp>, I thought it only
right to devote a column to the natural origins of a biological mechanism
that doesn’t involve the Y chromosome. Well, at least it doesn’t have to.
Needless to say, the subject of female orgasms isn’t exactly my cup of tea.
As a gay man, it’s always seemed rather exotic and foreign to me, sort of
like decorative basket-weaving in a small African village. As far as I know,
I’ve never even been in the same room as a woman having an orgasm, let alone
given a woman one.

Fortunately, a handful of dedicated researchers have spent a lot more time
on this issue than I have. Yet it’s fair to say that even these scientists
are still scratching their heads over the evolution of the female orgasm.
Before we get into the nitty-gritty, let’s make sure we’re all on the same
page about what a female orgasm actually is. A good working definition can
be found in a 2004 report in the Annual Review of Sex Research. According to
University of Texas at Austin psychologist Cindy Meston and her colleagues:

“Female orgasm is a variable, transient peak sensation of intense pleasure,
creating an altered state of consciousness, usually with an initiation
accompanied by involuntary, rhythmic contractions of the pelvic striated
circumvaginal musculature, often with concomitant uterine and anal
contractions and myotonia that resolves the sexually induced vasocongestion
(sometimes only partially), generally with an induction of well-being and
contentment.”

Actually, in light of that description and sans the female bits, perhaps
it’s not entirely foreign to me after all. In fact, in terms of evolutionary
function, women having orgasms with men is almost as puzzling as men having
orgasms with men. How many of us human beings were conceived in the wake of
our mothers having orgasms may never be known, but the same mystery doesn’t
surround our fathers’ orgasms that day. Unlike men, women don’t need to have
an orgasm in order to propagate their genes.

Thus, from a biological perspective, the “adaptive function” of the female
orgasm is still hotly contested. Some theorists, including the late and
legendary Stephen J. Gould , have claimed that it serves no purpose at all,
but is instead only a quirky, functionless by-product of the ejaculatory
response in males. In one of his cleverer pieces, re-titled “Male Nipples
and Clitoral Ripples,” Gould fleshed out an old argument first made by
anthropologist Donald Symons. In 1979, Symons noted that early in
embryological development, males and females share the same basic body plan.
As a serendipitous consequence of selection for male ejaculation (which in
straight men serves obvious reproductive purposes), some of the shared
connective tissue and nervous system pathways in females were “accidentally”
shaped for pleasure by evolution, too, leading happily to the occasional
orgasm in sexually mature females. The clitoris is essentially the female
version of the penis, since the two derive from the same embryological
substrate. This also explains why female orgasms are achieved more by
clitoral than vaginal stimulation.

Lest you think the by-product hypothesis was propagandistic, cooked up in
some musky faculty lounge by ivory tower misogynists, note that, for years,
the main advocate of this position has been a female philosopher of biology
named Elisabeth Lloyd. In fact, it was Lloyd who had initially given Gould
his lead on Symons’s thinking on the subject and who would later write a
book strongly endorsing the by-product hypothesis called The Case of the
Female Orgasm (Harvard University Press, 2005). Lloyd’s book was roasted by
many evolutionary thinkers because of the not-so-subtle feminist undertones
in her writing — basically she argues that female carnal bliss has been
liberated from the ugly realities of reproductive biology. Her position?
Ladies, go out — or stay home alone, your choice — and enjoy yourselves,
your sexuality is about more than just baby-making. But over the years,
other empirically minded detectives have been working on this case as well,
and many have begun to question the by-product account, claiming instead
that the evidence does indeed point to some possible adaptive function of
female orgasm.

So to help you play along in the role of orgasmic sleuth, here are a few
suggestive clues that researchers in this area have been trying to piece
together into a plausible evolutionary story:

Clue # 1: Twin-based evidence shows that orgasm frequency has a modest
hereditable component. That is to say, uncomfortable as it may be to think
of your flushed-faced grandmother writhing and moaning in ecstasy, there is
a definite genetic contribution to female orgasm. (To help “unsee” these
unsettling images shivering on the branches of your family tree, think on
the bright side: female orgasms tend to decrease with age, so we’re talking
mostly about only young, still-hot grandmas.) Hereditary factors account for
only a third of the population-level variance in female orgasm, however.

Clue # 2: Most women report that they are more likely to experience an
orgasm while masturbating than during sexual intercourse with a male
partner, and importantly such masturbatory orgasms do not always hinge on
simulating penile-vaginal sex. However, as University of Washington
psychologist David Barash notes, “just because something (e.g., female
orgasm) can be achieved in diverse ways (e.g., masturbation) does not argue
against it having evolved because it is particularly adaptive in a specific,
different context (e.g., heterosexual intercourse).”

Clue # 3: Furthermore, educated women are more likely to report having
masturbatory orgasms — but are no more likely to experience coital orgasms
than are less educated women. Religiosity is another social mediator:
religious women tend to have less frequent orgasms than nonreligious ones
(or at least they report having fewer).

Clue # 4: Using self-report data collected from college-aged American
females, researchers such as Florida Atlantic University psychologist Todd
Shackelford and University of New Mexico biologist Randy Thornhill have
uncovered a positive correlation between frequency of orgasm and the
physical attractiveness of male partners, with attractiveness being measured
by subjective ratings as well as by indices of facial symmetry. Recall that,
in “genetic fitness” terms, attractiveness tends to correlate positively
with health and overall genetic value.

Clue # 5: There is some physiological evidence that female orgasm leads to
the retention of more and/or better-quality sperm among a single ejaculate.
I don’t think I can put it any better than Birkbeck University of London
psychologists Danielle Cohen and Jay Belsky: “During the female copulatory
orgasm the cervix rhythmically dips into the semen pool, thereby increasing
sperm retention (by about 5 percent) relative to intercourse without orgasm,
along with the probability of conception.” But as Lloyd points out, most
references to these classic “data” on the “uterine upsuck” properties of
female orgasm derive from a single participant and were part of an old study
done back in 1970. Nevertheless, tellingly, a woman’s “desire to conceive”
leads to more frequent self-reported orgasms during sex, and female orgasms
are also most likely to occur during the most fertile period of the
menstrual cycle.

Clue # 6: In a recent study by University of Groningen psychologist Thomas
Pollet and co-author Daniel Nettle, Chinese women who were dating or married
to wealthy male partners reported having orgasms more frequently than women
whose partners made less. (“When having sex with your current partner, how
often do you have an orgasm?” On an ordinal scale: 1=never ; 2=rarely;
3=sometimes; 4=often; 5=always .) That is to say, male partner income
correlated strongly and positively with female orgasm frequency, and this
income effect panned out even after the authors controlled for (ruled out) a
host of extraneous variables, including health, happiness, education, the
woman’s personal income and “westernization.” In any event, women may not be
the only females in the animal kingdom whose orgasms are linked to the
status and wealth of their male sexual partners. Japanese macaque females
display the “orgasm-like” clutching reaction more often when they’re mating
with high-status males. There’s no data yet on whether or not they also bite
their lower lips in the process.

Together, these findings seemingly vindicate evolutionary psychologist David
Barash, a vocal critic of Elisabeth Lloyd who has been arguing that female
orgasm “is a signal whereby a female’s body tells her brain that she is
sexually engaged with a dominant individual.” Pollet and Nettle point out,
for example, that female orgasm may be linked to male income because money
(resources) is a reliable indicator of the male’s long-term investing in
offspring and it may also reflect desirable underlying genetic
characteristics. In this light, female orgasm may serve an emotional bonding
role, motivating sexual behavior — and hence conception — with high status
males.

I wish there were a climax to the story, but as you see, the tale of the
natural origins of female orgasm is a messy one. Some of the findings and
logic favor the by-product hypothesis, whereas recent data on male quality
and orgasm frequency cast reasonable doubt on the “functionless” accounts.
Female orgasm is unfortunately one of those questions that do not easily
lend themselves to controlled experimentation in the laboratory. One can’t,
of course, randomly assign women to have sex with males differing in status
and attractiveness to see if they orgasm or not (those pesky university
ethics review boards). So I leave it to you, dear readers, to cobble
together a once-upon-a-time story of female orgasm featuring the clues I’ve
left you.