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The beard cycle illustration: a virtuous circle is shown where beards being rare in society (on the left) makes them more desirable which leads to beards becoming more common in society (on the right), making them less desirable, which leads to fewer beards again. And so on...

The beard cycle

These days beards are in. There will come a day when beards are out. And a day when beards are back in again. That’s how it seems to go.

Turns out there is a name for this kind of thing: negative frequency-dependent selection. Essentially, the less common it is, the more useful a trait it is. As opposed to positive frequency-dependent selection which, as you can imagine, is the reverse.

According to this study, for example, when there are fewer men with beards in a population, they are judged as more attractive than when there are more of them. Hence they become gradually more popular until the effect starts to wear off and the clean-shaven look starts to appeal again. And round the cycle we go.

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