Wednesday, February 13, 2008

Valentine's Day Special: Scientific Lovers

Those of you in the Boston/Providence area can avail yourselves of a service that will match you with a partner based on your own DNA! It's science! Yes, on you can find a mate who is genetically compatible with you. Based on what criteria, you ask? What genes are examined? These questions and more will be answered in this Gateway Skepticism Valentine's Day Special: Scientific Lovers.

The site is actually very forthcoming with information. They've got a long page detailing their claims and the evidence for them. The first question they tackle is about the genes. What kind of analysis can they perform on genes to match you with a potential relationship?

Physical chemistry is based on the immune system. When we analyze your DNA, we look exclusively at your immune system genes. So, quite literally, when we say that two people have “chemistry”, we’re saying that their immune system genes are perfectly matched with each other.

By perfectly matched, we mean different.

After we analyze your DNA, we match you with other people who have different immune system genes from yourself.

The theory is that nature wants us to breed with other people who have different immune systems because it creates babies with a wider variety of immune system genes, and therefore, more robust immune systems—in other words, healthier babies.
That's what they do: look at genes in the major histocompatibility complex, MHC, and see how many you share with a potential mate. The fewer you have in common, the better matched you are with each other. It seems a rather simple metric considering the... well, rather sexy claims being made for the service.
When you share chemistry with someone, you significantly increase your chances of realizing these amazing benefits:
  1. You'll love their natural body fragrance--they'll smell “sexier” than other people.

  2. You'll have a more satisfying sex life.

  3. If you’re a woman, you'll have a higher rate of orgasms.

  4. There will be less cheating in your exclusive relationship.

  5. As a couple, you'll be more fertile.

  6. Your children will be healthier.

To me, these claims appear outlandish. However, my opinion counts for naught when references are provided for each claim. Yes, you read that correctly: it's a dating site that relies on published scientific research. Some of you might be pulling your credit cards out already, but let's examine in more detail first.
1. Chances are, you’ll love the natural body fragrance of your partner--they’ll smell sexier than other people
To back up this assertion, they cite an experiment in which women were asked to smell sweaty t-shirts worn by men. The relative rating by the women of pleasure of the smells was correlated with the difference in MHC genes between smeller and smelly smellee. A handy overview is given at the Wikipedia article for the author, Claus Wedekind.

This claim is actually pretty well established. It's a little weird, but could be true. If someone is matched to you by this service, you might like the smell of their sweat better than someone more similar to you in MHC genes—unless you're on the pill, in which case it's opposite. I wouldn't say it's enough to base a relationship on, so what about the other claims?
2. You’ll probably have a more satisfying sex life

3. If you’re a woman, chances are you’ll have a higher rate of orgasms

4. There’s a lower chance of cheating in your exclusive relationships when your DNA is matched properly
You may have noticed I presented three claims together—and what amazing claims they are!—and were wondering why. Well, as their primary support, these three wonderful sexy claims cite one and the same paper. That's right, on the same page that cites over 40 primary research papers and books, fully half of the amazing benefits of this DNA-matching service are resting on one published report. Let's read, shall we?

The paper (full reference below) can be found here. It approaches this question from a psychology perspective, administering a questionnaire about sexual satisfaction, cheating, etc. Honestly, I don't know enough about psychology research or statistics to know if there are any weaknesses in the study, save a few things.

First, the study involved only 48 couples. For such broad results, I would like to see something larger. Second, the participants were taken from a college campus and had mean ages 20.5 and 21.3 years for men and women, respectively. Hardly a representative group, especially for satisfaction in relationships and sexual behavior. Are 20-year-olds likely to be using a dating website? Third, I haven't seen any replication. Only three papers have cited this one (it is from 2006, after all) and none have checked the results.

None of these perceived-by-me weaknesses are deal-breakers for the accuracy of the study. It could be true that all three benefits of MHC-matching based on this paper and advertised by will come to you with a properly matched partner. But I wouldn't start a business around it, myself.
5. As a couple, you're probably more fertile
This is based on a few studies demonstrating that couples with dissimilar MHC genes have a lower rate of "spontaneous, unprovoked abortion." The studies appear pretty legit, but is having a lower rate of "spontaneous, unprovoked abortion" really the same thing as being "more fertile" as was claimed? The site is a little shifty about this point.
To be clear, they don’t show a correlation between chemistry and the ability to get pregnant. That wasn’t investigated in these studies, so they don’t disprove the correlation, either.
Riiiight. They don't say it'll happen, but they don't say it won't happen, do they?
6. Your children have a better chance of being healthy
This claim is extensively documented in humans and in other species. It seems obvious to me as a non-biologist who has scanned these papers that having many different haplotypes of the MHC genes will help prevent against some diseases and will possibly make the immune system better in general. This hypothesis has been tested and seems to be correct, again from a non-biologist's perspective.

I don't know about you, but I wasn't too convinced. The evidence for the good, fun stuff was a little shaky. Sure, having a slightly higher chance of healthy babies is great, but I'd really like to know more about the "more orgasm" thing. Can we get another study on that?

For those of you who have used or do use dating websites, maybe this one tickles your fancy. It certainly can't be any less scientific than some popular dating sites out there. I don't think it could hurt to give it a shot.

There's my Valentine's Day special skeptical gift: scientific analysis, tentative conclusions, and weak recommendations. It isn't romantic, it isn't a cure-all for your love problems, and it probably doesn't make blood flow to your naughty bits.

But it is the best thing I can give you: reality.

Full reference: Garver-Apgar, Christine E, Steven W Gangestad, Randy Thornhill, Robert D Miller, & Jon J Olp (2006) “Major Histocompatibility Complex Alleles, Sexual Responsivity, and Unfaithfulness in Romantic Couples,” Psychological Science, vol 17, no 10, pp 830-835.


Old sliderule geek said...

So if I have children with someone whose armsweat smells the best then my children are guaranteed to be healthy? I have three healthy children, but I guess I was unscientific and never smelled my wife's armsweat before we got married. See, love does conquer all! And that's an unscientific moral for Valentine's Day

The Jackdaw said...

I'm having trouble reconciling the 'immune system match' to the 'fragrance endearment' leap. Correct me if I'm wrong, but I think the possibility of genetically-healthy babies does not (automatically) guarantee a life-time of romantic fulfillment.

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