Friday Weird Science: Why cunnilingus?

Jul 12 2013 Published by under Friday Weird Science

Humans are infuriating creatures. We don't ever just want to know how. Or when, or what. We want to know WHY. WHY is the sky blue. WHY do we search for the Higgs Boson. WHY is blood red. WHY do people perform cunnilingus. Deep questions, man.

But for these deep questions, there is SCIENCE. And so these authors set out to answer this deep, deep question. Why cunnilingus? What is the evolutionary purpose? After all, we can't possibly be doing this stuff just because it's fun or nothin'.

I would first like to note: there are some problems with this study, yes. But there is one thing I like about it. It turns out, the second half of their results don't support the hypothesis. And the authors admit it, and PUBLISHED IT ANYWAY. You go, guys.

That said...I'm not so sure about the findings of their first hypothesis either. But we'll get to that.

Anyway, these scientists (and, I would like you to know, unlike other evo psych studies I have seen, they are NOT all men!!! 50% female representation) were interested in the purpose of cunnilingus. Why does it exist? What's it for? It's can't just be, you know, for good times or anything. They hypothesized that it served a purpose, and the purpose they believed it filled was securing your mate. They also hypothesized that it might help with the woman retaining sperm in her reproductive tract.

Where do you get these kind of hypotheses? Well, the first hypothesis, of securing your mate, comes from a whole pile of previous evolutionary psychology literature on the topic. The whole idea is that attractive females are in danger of being lured away by other males, so men have to adjust their behaviors to prevent cheating as much as possible. Previous studies have backed this up by noting that men want to have sex more, thrust harder, and ejaculate more sperm when they've been away from their partner for a while (I will get to my own concerns about this further on). So the idea here is that men want to keep ladies happy to keep them from straying, and therefore, they will give them cunnilingus to keep them happy.

What about the second hypothesis? The idea of "insuck", as it were? The concept is this: over a long time now, people have wondered about the purpose of female orgasm. What is it for? Is it a byproduct because men can have orgasms? Is there a genetic basis? One hypothesis states that the purpose of female orgasm is "insuck", that during and after female orgasm, the cervix comes under negative pressure, sucking sperm up into the uterus and aiding fertilization. If this is actually the case, then cunnilingus, and promoting female orgasm very close in time to male orgasm could (in theory), increase the potential for fertilization by sucking up the sperm.

To test these two hypotheses, the authors recruited 243 men in the US and Germany, and asked them some questions: how attractive is your partner (to you and to others), how often do you bone, how satisfied are you in your relationship, and how often do you perform cunnilingus.

They then performed a lot of data analysis that looked as "risk of sperm competition" for infidelity in the ladies (whether other people found her attractive), and how often the men performed cunnilingus. They found a correlation between the "risk of sperm competition", and how often men performed cunnilingus. The authors concluded that this means that sperm competition is a reason for performing cunnilingus, and that cunnilingus is therefore a way of securing the fidelity of your partner.

But what about sperm retention? That's more difficult. To assess that, they looked at the time between male orgasm and female orgasm (estimated by the men as they filled out the survey, which probably does not say a lot about its accuracy). IF cunnilingus for female orgasm would help sperm get along, then presumably it would be better for the guy to ejaculate as soon as possible after cunnilingus to get the sperm in there. In fact, only about 40% of the men involved did, and so the hypothesis was not supported. The authors conclude that, while cunnilingus is good for securing the fidelity of your partner, it's not a good sperm retention device.

Now, let's talk about the issues with this study:
1. The sample. First off, self report, and no man wants to seem...ungenerous, as it were. Secondly, the sample was recruited so that people were in long term relationships. People in long term relationships get comfortable. Plus, if the idea is ensuring mate fidelity...wouldn't you want people who were in new relationships? Ones where they were anxious to please and who were less assured of fidelity rather than otherwise? The sample is also a classically WEIRD one, mostly from the US and Germany. Do people in all cultures perform cunnilingus? I'm not sure they do, certainly, historically, it was frowned upon in many cultures. And if they don't...doesn't that take away some of the evolutionary necessity?

2. I actually am not sure about one of the hypotheses that this entire thing is based on, that men are more likely to please women when there has been "opportunity for infidelity". The usual example of this is long distance. When a man is away from his partner for a while, when he comes back, he tends to ejaculate more sperm, want to have sex more, and be more likely to attempt to please his partner. The usual way evolutionary psychologists like to explain this is because the female partner had opportunity for infidelity and therefore the guy has to get his in on the offchance that she's been screwing around. I actually think that, when a man has been away from a woman for a few days, there might be another explanation.

Because he HASN'T HAD SEX IN A WHILE. That might come as a shock. As far as I can, surprisingly, no one has tested this. This seems pretty simple, get a bunch of people (maybe, say, scientists at a conference!) who are away from their significant others. Get the men who are married to/in committed relationships with women. Divide half in to the 'masturbate' group and the other half into the 'suffer' group. While they are at the conference, the masturbate group releases their feelings, and the suffer group...suffers. When they get back, get relevant recordings from the first sexual encounter, a sperm sample (if you can), desire scores, and attempts to please partner, etc. This would tell you whether this is an issue of "opportunity loss" where the woman had a chance to cheat or whether the guys are just a little...impatient, you know.

3. Cunnilingus has a male counterpart: fellatio. What purpose does THAT serve?! After all, swallowing probably doesn't make babies. I think, while of course this study isn't meant to test it, without consideration of fellatio they are lacking a good bit of context.

4. Part of the measure of "risk" the authors took was how hot the men thought their lady was. They took this as a measure of risk because hot women would be more likely to be lured away by other men (because, of course, these women are just waiting around to be lured, not like they have any thoughts of their own on this front). I think this measure is going to be incredibly biased. Aside from the fact that this basically turns women into bodies which can be lassoed off to someone else's cave, or whose cold, calculating eyes are forever sizing up other dude's biceps for their own potential advantage, there is another issue with this. Maybe they want to have sex with her more because she's ATTRACTIVE to them. All the men in their sample were in committed relationships of some duration. They were all having sex at least once a week. OF COURSE they are going to think their partner is sexually attractive. They are HAVING SEX WITH HER. I think using a measure of attractiveness as a measure of "risk" probably grossly biased their numbers. I think they had just stuck to "risks" like evidence of prior infidelity, they probably would have lost all of their significance.

So I wonder about the basis for the argument. While cunnilingus may be a good mate bonding strategy, I don't think it's really more likely because you're pretty sure she had sex with someone else, or could have sex with someone else, or is looking to have sex with someone else. Shockingly, I think it could be possible that cunnilingus is a good mate bonding strategy because...it's fun. And people like it. And many women cannot have sexual pleasure otherwise. Maybe it's a mate bonding strategy, sure, but maybe it's also a good time.

16 responses so far

  • dr24hours says:

    As my girlfriend lives in a distant city, and I only get to see her about every other week, I'd be willing to volunteer for the study you propose.

  • nccomfort says:

    Great example of the fact that science isn't actually very good at "Why?" questions. As I think Ernst Mayr said, science is good at "How?" questions. Leave the whys to the philosophers.

    Or as the mountaineers say, "Why? Because it is there."

  • Jc says:

    What if it is just an exchange of bacteria for our micro biome ?

  • Book says:

    Pair bonding. I do what I can to keep her/myself happy with the current situation (or to try to improve it)

  • Hermitage says:

    Wait, an I having a reading comprehension fail...or did they conduct an entire study on cunnilingus without surveying women AT ALL?

    • scicurious says:

      YES. YES. THANK YOU. I've been looking for this nagging issue that was bugging me. This was it.

      • ET says:

        But of course! Why ask women - we are objects to be acted on, not active participants nor would we take any initiative...

    • Munkey says:

      The question is dealing with why men perform oral sex on women.

      How can women answer that question? "I like it so I ask my man to do it and he does it for me."

      ET - get past your conspiracy theory of sexism.

      • scicurious says:

        But to ask their question about pair bonding, wouldn't it make good sense to ask the woman "does cunnilingus make you feel closer to your partner" as compared to other kinds of sex. It would also be good to ask the women when they end up receiving the most cunnilingus, to see if it jives with what the men say, and to check up on numbers. Finally, it would be important to ask the women questions about cheating (part of their hypothesis), how likely they are to cheat, how attractive they feel they are to other people, etc. There are many parts of this study that could have gotten more strength just from asking the women.

  • Jen says:

    Why does every single little bit of human behavior need to be dissected and explained in terms of how it pushed forward our evolution? If it didn't HURT our survival or reproductive chances, there was no pressure against it.

    Can't it just be that we do it because it's fun?

  • H says:

    There was a study done using photographs to determine the attractive features in people (male and female) I believe that they found out that symmetrical faces were more attractive (as they're more fertile?).
    Another study looked at the clothes women wore & how attractive they were, (I think this may have been included in a Prof Robert Winston documentary, The Human body maybe?), they appeared more attractive to men when they were about to ovulate & this was reflected in the clothing that they chose.
    Could photographs/ video tape (with/ without them speaking be included in a further study?) Having said that with the video other questions may arise eg Body language (& attractiveness).
    A few final thoughts, your study has considered how attractive the females are, but what about how attractive their male partner is, could this be a factor in their fidelity as well? Should attraction be considered entirely about physical appearance? - I'm not sure on this last one, initially it's appearance (before you speak), but... Finally, what role(s) do hormones play in this, as the study had long term partners, do they have children? I'm sure I have read/ heard about hormonal (& physiological?) changes in both males and females when children are born. I suspect I have thrown up more questions than I've answered... But that is what science is about right? 🙂

  • [...] they’re invariably sexist nonsense, especially when the topic is anything to do with sex. But Friday Weird Science: Why cunnilingus? valiantly unpacks such a study without losing the plot and it makes for an interesting [...]

  • Charles says:

    Did I miss it or has this article overlooked the fact that there are many men who receive as much enjoyment performing cunnilingus as their recipient partners?

    Numerous males actually PREFER this activity to 'normal' in-and-out sex.

    To counter any argument that m/f oral sex might have an evolutionary basis, I don't think that lumping this practice together with anal sex would be stretching things too far. (Innuendo unintended:-)

    Again, there is a not insignificant number of heterosexual males who prefer this activity, at least occasionally, in some cases, exclusively.
    No doubt to a far lesser degree, but it is certainly not rare for females to site anal sex as 'their thing'.

    If the categorising of oral with anal sex is valid, which I contend it is, there seems little chance of there being any validity in an evolutionary (increased procreation), argument .

    Perhaps applying words such as variety, novelty, even experimentation, to such pastimes would assists with any further analysis of 'why'.

  • Timfin says:

    Mjchael Douglas stated his throat cancer was associated with muffin munchin' in sperm competitive relationships. I wonder how this will affect todays activities.

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