Saturday, February 11, 2017

The Evolution of the Clitoris

In my last post, I talked about an impressive online program at that teaches users a wide variety of techniques for using the fingers to stimulate the clitoris, get a woman aroused, and help her have an orgasm.  Knowing how to do this is important for those of us with clits and for those who love us because so many women – over 70% according to many studies – are unable to have an orgasm from normal penetrative sex alone, without any direct or indirect stimulation of the clit.

But this raises the obvious question:  why is that true?  If the purpose of the clit is to make sex pleasurable and lead to orgasms, why isn't the clit positioned so that it is directly stimulated during normal, penetrative, penis-in-vagina (PiV) sex?

Lots of theories, not much evidence.

Human evolution has a lot of puzzles, and the origins of our mixed-up mating system and our dysfunctional menstrual & childbirth system are two of the most fascinating. Unfortunately, there's not a lot of hard evidence, so we're left with ingenious ideas using analogies with other evolutionary patterns.  Sometimes, as we will see, a plausible-sounding idea can be disproven, but rarely can a good one be conclusively demonstrated to be "true."

Still, the process of coming up with good possible explanations can be entertaining and illuminating, as long as we keep in mind that these are only hypotheses, not definitive answers.  With that caution in mind I'm going to indulge in a little bit of detective work and theorizing about an enduring mystery:  why is the human clitoris positioned so that it isn't directly stimulated during normal PiV sex?

The clitoris is the only human organ whose sole function is pleasure.  It's incredibly sensitive, with more than 8,000 nerve ends packed into a tiny space.  It exists solely to be rubbed, licked, sucked or otherwise stimulated, to create pleasure, sexual arousal, and orgasms.

We associate orgasms with PiV sex and reproduction because the male orgasm is necessary for ejaculation and conception.  But if PiV is the only kind of sex we have, then the majority of women will seldom or never have an orgasm with their partners.  This leads to the well-known "orgasm gap," the finding that among single people who are having sex, men are 4 to 7 times more likely than women to have an orgasm in a given encounter. Even among long-term couples, men are roughly twice as likely to have an orgasm.

Now, we could explore all sorts of interesting social and cultural tangents here, like why don't more men spend enough time on foreplay and why don't more women demand it?  But let's stick for now with the underlying evolutionary puzzle, that an organ that appears to be designed for one specific purpose also appears to be poorly located for achieving that purpose.

Function versus random variation

One basic principle of evolution is that if you see a lot of seemingly random variation in a feature, the specific details affecting that feature are probably irrelevant in functional terms (though they still may be relevant for sexual selection).

For example, having fingerprints is useful.  The ridges on the skin increase your tactile sensitivity and improve your grip, particularly for wet, hard objects.  But the specific pattern of lines and whorls makes no difference, so that pattern is free to vary randomly.  In fact, it varies so much so that every fingerprint is unique or nearly so, which is why fingerprints can be used for identification.

In a similar way, clits and inner labia vary widely in size, shape, and color – and why not?  It's not like they have to fit into a certain receptacle or perform a function related to size or shape.

However, there does seem to be one functional difference.  The gap between the clitoris and the vaginal opening is inversely related to the likelihood that a woman can have an orgasm from PiV alone.  The bigger the "clitoral/vaginal gap," the harder it is to have an orgasm without explicit clitoral stimulation before or during PiV sex.

Specifically, a gap of more than an inch means that a woman is much less likely to be able to have an orgasm from PiV sex without clitoral stimulation.  A gap of less than an inch means she is more likely to have easy PiV orgasms.

If this really mattered to reproduction – if, for example, having easy orgasms increased your desire for sex or improved your chances of getting pregnant – it would seem that we would all be descended from women with clits near their vaginal openings who orgasmed easily from PiV.  Obviously we aren't, or all women would have short c/v gaps, but why doesn't it matter?

Does the female orgasm increase fertility?

Associating orgasms with conception seems so plausible that scientists have made many attempts to find out whether orgasms during PiV sex increase fertility.  One of the most plausible and persistent hypotheses is called the "upsuck theory," the idea that a well-timed female orgasm might cause semen in the vaginal canal to be sucked up into the womb.

However this idea has been investigated and disproven repeatedly, as have all of the other theories about orgasms and conception.  Data collected on large populations consistently demonstrates that women who never orgasm during PiV are just as likely to conceive during sex as women who always do.  The female orgasm does not enhance fertility or increase conception rates.

Instead it seems like the variation in the c/v gap is either completely random, or else we're evolving in the other direction, toward a larger c/v gap.  And this creates a bit of a mystery.  Why doesn't evolution favor women who have an easier time orgasming during "normal" reproductive sex?  Wouldn't the extra reward cause them to have sex more often, and thus have more babies?

The answer, surprisingly, is that they might (or might not) have more sex, but it doesn't matter in evolutionary terms.  And to understand what's going on we need a bit of background.

To begin with, humans have sex FAR more than necessary to ensure that females get pregnant.  Compared to most other mammals, we're sex maniacs!  We have sex when we aren't fertile. We have sex even when we're pregnant!

We have even evolved a unique combination of features – cryptic ovulation and full breasts for non-nursing women – whose purpose is to ensure that we will have sex even when it is reproductively meaningless.  For most mammals, it's easy to tell when a female is ovulating and able to get pregnant.  For humans, it's not.  And for other mammals, full breasts are always a signal that the female is not fertile.  But not with humans.  For us the "not fertile/not interested" sign is completely inverted and turned into a sexual attractor!

Humans are weird because, for us, the primary purpose of sex is not conception.  It is pair bonding.  We have sex all the time, especially when we aren't fertile, because the attachment between man and woman is so important to our children's survival chances. We can and often do have sex all the time, even when we're pregnant, nursing, menopausal, or simply in-between the fertile points in our periods. And that is crucial for maintaining that bond.

The key point for understanding why this is true is that human evolution is NOT driven primarily by the conception rate.  For long-lived creatures, we have very few children.  Even among "primitive" tribes, the average birth spacing is 3-4 years unless a baby dies in infancy.  And it's extraordinarily difficult for us to get pregnant.  Most non-domesticated mammals have 90 to 99.9% pregnancy-per-ovulation rates under normal circumstances in the wild.  With humans, it's around 20%.

The explanation for this comes from the harsh reality that having large-brained babies makes pregnancy extremely risky for human mothers.  The fact that human infants are also helpless for a long time means that every pregnancy is both a risk to the mother's life and a potentially huge investment in parental time and calories.  So a "wasted" pregnancy – one that doesn't produce a successful adult – is very expensive in evolutionary terms.

This means that a woman's chances of having living descendants many generations later went up if she had several healthy, successful adult children.  And in an environment in which only a quarter of all children made it to adulthood, having lots of wasted pregnancies meant a lower, not a higher, evolutionary success rate.  The big evolutionary filter was not ease of conception or the total fertility rate, it was the infant and child mortality rate.

This means that for our ancestors it was better to get pregnant less often and to devote more resources to raising each kid, and it was critical to have the best possible genetic material  for each kid.  Indeed, it appears that one big reason for our extremely low conception rate is that the human menstrual system evolved to create an extremely hostile environment for the fertilized egg, specifically to kill off as many sub-par embryos as possible.

But what constitutes "the best possible genetic material"?

As humans evolved, the critical traits were:  general fitness, robust immune system, intelligence, language, and sociality.  The first two are standard for all "higher" animals, but the last three are special.  In prehistoric times, a lone human was a dead human.  We're among the most intensely social species on earth.  Humans depend as a species on cooperation, communication, and intelligent problem solving.  That's our evolutionary niche, and so far it has been a great success.

Among surviving tribes of foragers/hunter-gatherers, a man was most likely to have great-grandchildren if he was smart, verbal, and cooperative, and did everything he could to help his kids and grandkids survive and grow up.  So women who favored men who were good fathers also had more great-grandchildren, and those great-grandchildren also had better chances of reproductive success.

Okay, fine, but what does this have to do with the clit?

Well, one of the most interesting theories about the clitoral/vaginal gap is that it functions as a selector for all three essential human traits.  The idea is that a man who wants to please his partner and make her happy (cooperation), who can understand what she's trying to tell him (language), and who can figure out how to give her an orgasm using his hands and mouth (intelligence), is probably going to be a good father, and his kids will inherit those traits.

If a woman has a short c/v gap, she can have orgasms with almost any guy.  But if she has a long c/v gap, orgasms are not automatic, and she is more likely to prefer a guy who can "solve the puzzle of the clit" and make her happy.  In the process, these women are more likely to dump the less social/verbal/intelligent guys who are "bad in bed" and have their babies by the guys who are better dad prospects.

And isn't that what we still see today?  Women start off being attracted to the big, strong, healthy guys.  But the orgasm gap in the teens and early 20s is huge.  About 10-20% of young women can have orgasms routinely with almost every partner.  But a lot of the rest feel like failures and are chronically dissatisfied with sex because they rarely if ever reach orgasm.

Gradually, however, many of the women who can't have pure PIV orgasms do eventually find guys who are smart enough and who care enough to "solve the puzzle" and learn to give pleasure and orgasms to their partners consistently.

These men are the ones that women call "keepers."  They are givers – good, generous lovers who are also, on the average, better life-partners and better dads.  So, paradoxically, being a little harder to please sexually may make a woman slightly more likely to end up having kids who grow up and become successful adults.

The important thing to remember about this is that evolution is a blind statistical process. All that matters is whether a gene or combination of genes leads to having a larger or smaller number of descendants many generations later.

Specifically, it does not matter to evolution whether something makes you happy or makes life easier or more enjoyable.  It is not a benevolent process.  It it is not affected at all by human pleasure or suffering or frustration unless those things result in having more or fewer descendants in the long run.

So it makes perfectly good sense for evolution to favor something that makes it harder for us to get pleasure from sex, provided that there is a long-term reproductive payoff.  In this case, it makes sense for women to have a reason to prefer having sex with men who are smart and willing to please if it means that those women are even slightly more likely to have babies who will grow up to be smarter and more cooperative, and who will choose or be chosen by smarter and more cooperative partners ... and so on, down through the generations.

But note that if the c/v gap was one of the things pushing evolution along toward brainier and more cooperative humans, it could only work if women really valued clitoral stimulation and orgasms.  It’s not enough to have a puzzle.  Women have to care a lot and have a strong preference for the guys who actually solve the puzzle.

So this theory isn't just an explanation for the c/v gap.  It also explains why the clit is so rich in nerve ends and why women's orgasms feel so good!

As I said at the top, this is just one possible explanation for the c/v gap.  But I think it's a good one.

So, ladies, when you insist on your partner helping you satisfy your needs and not just his own, and you dump the guys who won't or can't reduce the orgasm gap, you are part of what appears to be a long tradition with a strong evolutionary foundation.

And men?  If you put your lady's pleasure first and take pride in your mastery of good clit technique, then congratulations.  That means you're taking your rightful place in a long line of winners in the evolutionary race!

Or at least it's fun to think so, and sticking to those standards will greatly improve the quality of sex everywhere!


1 comment:

  1. I've only recently read about the c/v gap, but this is the first article that gives some kind of plausible explanation about pleasure and evolution.
    Thank you