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I head west for a couple days and Chris up and creates a commotion… Of course he’s absolutely correct to do so. Coyne is entitled to his perspective, but in no way does he speak for science. But since we’re on the topic of Jerry Coyne, it’s good reason to bring up another idea of his that hit my radar recently. Readers know I’m exploring science and sexuality for my next book, and earlier this month I received several emails alerting me when Coyne shared his theory about the adaptive significance of semen flavor.
It is the conventional wisdom in human sexuality that semen tastes bad. Anyone with minimal sexual experience knows that although many women will perform fellatio on their partners, most bridle at the thought of swallowing the ejaculate. Its flavor is frequently characterized as revoltingly bitter or salty. The “swallow or spit” dilemma faces any woman who performs such an act, and whose partner regards swallowing as a gesture of love.
I’ll admit I was a bit surprised when the post hit my inbox, but since we’re reading Bonk, it’s an appropriate subject and one I have not considered before. Coyne took an informal poll by enlisting Dr. Fawzia Rasheed to ask her female acquaintances:
Sperm…would you spit or swallow? In other words, can you abide by or do you hate the taste?
Here are the results reported:
There were sixteen responses, many including pungent asides that I cannot repeat on a family-oriented website. One answer was a non-response (”I should be so lucky”). The other fifteen included eleven “spits” and four “swallows”. But among the latter, two women commented that they did not like the taste: one, in fact, swallowed to get rid of the flavor as quickly as possible. Two others said “swallow” but did not comment on whether they enjoyed it. Therefore, 13/15, or 87% of informative respondents could not abide the taste of semen.
Coyne goes on with his theory:
Natural selection maintains the repugnant taste of semen so that a man’s sperm will wind up in the appropriate place: the vagina and not the stomach. So long as sperm tastes bad, women will not be tempted to swallow it, but will turn their male partner towards conventional intercourse, which of course is the only act that will produce children. In other words, any male with good-tasting sperm would have fewer offspring than his competitors. A man whose sperm tasted like honey would probably not have any children at all.
Perhaps. But, I suspect there’s more going on with both this poll and the evolutionary significance of semen flavor. First, there are social norms and cultural mores for our behavior and receptivity to sexual activities. Also, there’s no question that bitterness is influenced by diet and the flavor is subject to a recipient’s individual preferences. It’s also possible taste provides females with valuable information about the health of her partner and potential fitness of future offspring if they couple. And then I’m highly suspect of the mode of inquiry for this particular poll and the degree to which Dr. Rasheed’s acquaintances felt comfortable responding to Coyne’s question. Were they aware it would be reported back to him and do they know Coyne personally? Is Rasheed a close girlfriend and confidant or possibly their graduate advisor? I also expect that arguably the most significant influencing factor is the level intimacy in the relationship between people involved in the, errr… transaction.
While Coyne offers two impossible ways to test his idea, let’s just say that I have trouble swallowing the hypothesis.
April 28th, 2009 at 3:29 pm
Straw man. Coyne wasn’t trying to speak for science.
And speaking of “speaking for science”! Heh. Let’s hope Chris wasn’t trying to with this!
Good god!
A commenter over at PZ’s site named “Sigmund” responds best…
‘Nuff said.
April 28th, 2009 at 3:36 pm
Hahaha. Great post! And tip of the iceberg with problems associated with his idea.
I saw this from Coyne and couldn’t believe how ridiculous he came across. But it was past April Fools. Oy.
April 28th, 2009 at 4:21 pm
Wouldn’t it make more sense to discuss the evolution of taste itself in humans? Seems to me that any compounds that influence taste in semen actually evolved to “help” sperm survive the trip in a hostile environment on the way to the egg, not to ostensibly say, “oops! wrong hole!”.
April 28th, 2009 at 4:46 pm
Coyne’s theory is interesting although as Michael notes, the taste may be because of the compounds that enable the sperm to survive; the taste may have an ancillary effect on promoting vaginal intercourse and Coyne may be making the common adaptionist mistake. At this point it’s best to devise testable and falsifiable experiments for his theory.
I also remember there being some study which reported that the expulsion of semen into the vagina cause the release of endorphins that soothe and calm. Wonder what happened to that one.
Also, do you know what Kinsey and Masters & Johnson say about this? I cannot believe Kinsey never asked his thousands of interviewees what they do with semen in their mouth.
April 28th, 2009 at 5:53 pm
Thanks for bringing this up. I was thinking of you guys when I read this. Articles like this distort natural selection. Even if women have been swallowing since the dawn of humanity, it is unreasonable to assume they are doing it at the exclusion of standard intercourse. I fail to see how a woman who swallows would have less children than a woman who didnt. Or, how a man who tasted bitter would have less children than a man who doesnt.
April 28th, 2009 at 8:40 pm
Per Michael’s comment, I’ve read (somewhere) that primate semen is a “witches’ brew” of chemicals designed to facilitate fertilization, influence female body chemistry, and probably to cause problems for sperm competition with other males. I think strong chemistry is probably a greater driver for strong taste than Coyne’s hypothesis.
Wikipedia to the rescue: ” Basic amines such as putrescine, spermine, spermidine and cadaverine are responsible for the smell and flavor of semen. These alkaline bases counteract the acidic environment of the vaginal canal, and protect DNA inside the sperm from acidic denaturation.”
http://en.wikipedia.org/wiki/Semen
April 28th, 2009 at 8:55 pm
I think CuriousWavefunction has it right – Semen is slightly basic likely as a result of the acidity of the vagina (likely due to cutting down on wee mircobial beasties) and it was a different evolutionary pressure that caused basic things to taste bad to everyone, not just females. As in bases don’t do very nice things to the ‘ole GI tract. (Versus acids which have no problem, which is probably why you don’t have conventional wisdom on vaginal secretions tasting bad, unless there’s pathology.)
Besides, wouldn’t the female orgasm be a much more effective evolutionary pressure to prevent the “whoops wrong hole” action? Furthermore, if the reproductive uselessness of oral sex is the evolutionary pressure here, then why do men still like fellatio so much (granted almost never to the exclusion of vaginal intercourse)?
Sorry, Coyne, that dog won’t hunt.
April 29th, 2009 at 12:21 am
While there’s not much in the way of a poll there, I’m surprised that the survey didn’t include gay men. If there’s a notable difference, that would certainly be worth reporting.
April 29th, 2009 at 3:03 am
*yawn* I wonder if Jerry’s just trying on a really lame joke with the “bad taste encourages this behavior instead”.
April 29th, 2009 at 3:13 am
Heres my theory :
women who like sperm have children
women who dont like sperm they dont have children
try to beat that
April 29th, 2009 at 11:42 am
Cant’ beat your take Ed. But I actually htink it is an interesting idea to explore. Human sexual practices have evolved in many directions, and one has to wonder how much is natural, and how much is nurtured or cultural. Would the results be the same in Africa, or the Middle East? Who knows.
But I am intrigued by the notion that response to taste in this “arena” might well be influential of reproductive success in some way.
April 29th, 2009 at 5:46 pm
Honestly, the taste is so varied from guy to guy depending on diet, does he smoke, take drugs, drink, etc… I think Coyne’s theory and “survey” are nigh unto useless.
Seriously, Dan Savage has dedicated numerous “Savage Love” columns to how to alter the taste of your lover’s sperm.
April 29th, 2009 at 6:45 pm
This reminds me of when, after I switched from ecology to physics, my then girlfriend came back from a bio class with the definite assertion that human beings sweat because our ancestral lemurs secreted packets of salt as a grooming reward. She knew that one would drive me crazy, so she had a little smile when she told me. Coyne is in that territory here.
April 29th, 2009 at 10:53 pm
I ROFL-ed when I read the semen “theory” by Coyne a few days ago (and yes, I tweeted the link so others could laugh, too). A great satire of the ridiculousness of Just-So-Stories of Evo-Psych.
April 30th, 2009 at 1:03 am
[...] Here’s a controversial topic to cover on a blog: The Adaptive Significance of Semen Flavor. [...]
May 2nd, 2009 at 9:34 am
What bothered me the most about Coyne’s column is that the analysis can be taken and flipped around. Coyne assumes for no good reason that if semen tastes well it shall end in all the wrong places. However, even if it were true that men whose semen tasted better ended up ‘loosing’ some of it down their lovers throats; it does not necessitate that they will thus forgo copulation. That is, one could argue – that there is an advantage to better tasting semen – as women would be more willing to engage in sexual activities with those men (both oral and vaginal). So, I am somewhat distraught because explanations that appear to make sense and that appear plausible can be completely overturned. In the filed of evolutionary psychology we must tread carefully for we are too liable to fall prey our own folly and prejudice.
May 2nd, 2009 at 7:31 pm
I am quite surprised to see so many people here taking Coyne at face value. His post was a SATIRE, a good one, too. People were linking to it and laughing and high-fiving all over twitter last week. Exposes brilliantly the emptiness of EvoPsych co-called “methodology” as well as motivations.