Do Humans Have a Mating Season?

BlogHer Original Post

I can't help it, I read the abstract of Markey et al. Seasonal Variation in Internet Keyword Searches: A Proxy Assessment of Sex Mating Behaviors in Achives of Sexual Behavior and just...

But fear not, horny teenagers everywhere! You now have a scientific excuse for wanting to get it on in the hot days of summer. And the cold nights of winter. For all the horniness during spring and fall? Sorry, you're on your own.

Have you ever wondered if your horniness varies with the seasons? If you're more inclined to mating behavior, say, in the fall or something? After all, other species have "mating seasons." Presumably this wouldn't apply to us, as females of the human species are available for mating much more often than once a year, but is there seasonal variation anyway?


Photo by See-ming Lee. (Flickr)

There are seasonal trends in things like when babies are born, for example. Babies are conceived more frequently in December (though it's not by much), leading to a rash of fall birthdays. There's also an increase in abortion in the winter months.

But it's not just winter. If you go by condom sales, there's a bimodal peak in the winter and summer, and a similar pattern in STD diagnoses (whoops). So if you take all this together, people hypothesize that we have two "mating seasons" in the winter and summer.

Why these increases? Various hypotheses have been proposed, including things like better sperm during those times (all the delicious food?), the holiday mood, and ... tax laws (hey, there's no accounting for taste).

But of course, this is all sex that we KNOW is happening. We know cause there are condoms and babies and STDs. But what does this really mean about mating behavior? Are people really seeking out mates? Or just loving the one they're with?

To find this out, the authors of this study bravely turned to Google. They looked at the numbers of times that people searched for three indicators of mating behavior: porn, prostitution, and mate-seeking (via dating websites). Why these three? Well, they wanted to separate out a potential difference between sex seeking and mate-seeking (porn and prostitution versus dating).

Is it an increase in mate seeking? Or are we just more horny? To make sure it's not Google searches themselves that vary seasonally, they picked a bunch of control keywords to compare, including things like pets, popular websites like Yahoo, and car references. I have to say I wish they'd reported the car trends, I really want to know if those vary seasonally. Just because it'd be so odd.

What you can see here is the relative search value index for porn, from 2006 to 2011. They superimposed a six-month harmonic cycle, and found that the six-month cycle accounted for 16 percent of the variation. So people are (slightly) more likely to go on a porn hunt in summer and winter (though to me it looks like the summers account for this more than the winters, and WTF happened in fall of 2009? Something depressing?).

But the series for prostitution is much more striking.

And so is the one for dating sites.

Taken together, it looks like there's a six-month cycle, and the "vacation and holiday effect" is in force.

Of course, Google trends (what they used to look at the data) doesn't include things like the gender of the searcher, so we can't tell who's driving the searching changes. And while it provides a search value index, it doesn't provide the actual number of searches, which would be a bit better for the data.

So what's causing the increases? Well, the authors call it the holiday effect. Summer and winter? Those contain holidays. Vacations. Free time. The time in which you're not constantly swamped with work (presumably), and the time when it's almost aggressively forced on you how much people are VERY MUCH ENJOYING their Christmas or beach vacation or New Year's or international travel. And often, they are enjoying it with their significant other.

There is also a big notch up in weddings in the summer. The increase in social pressure might drive you to seek sex or mating, increasing the frustration that you normally feel by adding that extra dose of self-pity. So if you find yourself searching for "xxx," "boobies," or hovering over a Match.com profile, stop and think. Is it those summer or winter nights? It's possible! And then keep searching, after all, the season can't stop you! And oh, those summer (and winter!) nights.

Scicurious is a blogger at Scientific American The Scicurious Brain and Scientopia's Neurotic Physiology, where this post first appeared. She has a PhD in Physiology, and is currently a postdoctoral researcher. She loves science, and so should you.

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