Burn Notice: Why Chilis Taste Hot

05 Jun

I love schadenfreude, that special feeling of watching someone else’s misfortune. Ninety percent of the internet runs off it. Youtube is full of videos of luckless skaters and instant karma. A good amount of chili pepper videos exist too (to my eternal entertainment). Like this one:

Love it. But if you think about it, it does bring up an interesting natural question. Why are chili peppers so hot?

When talking about evolution it’s useful to think of answers as either hows’ or why’s, a.k.a. proximate or ultimate. How a chili gets that hot, the proximate cause, is simple. The flesh surrounding the seeds is packed full of a chemical called capsaicin. Capsaicin is an odorless, fatty compound and, once in your body, binds to the same cellular receptors that detect heat. That’s why it tastes so hot, your cells literally think they’re in danger of burning up.

But the ultimate cause, the why, is pretty interesting too. Why is the fruit so full of capsaicin? Chilis are a fruit after all, and fruits exist to be eaten, but most animals would shy away from something to distasteful. Why would evolution put so much energy into creating something that defeats its own purpose? Well it, turns out that not all animals shy away from the capsaicin. Birds in particular have different heat receptors than we mammals do, meaning they can’t taste the heat.

Think about it. Pepper seeds are pretty flimsy and soft. A big old mammal, like a cow, that grinds its food to a pulp would totally destroy the precious seeds. But birds tend to eat things whole. The seeds can pass through their digestive tract unhurt. A pepper’s fire is its tool. Its evolved over generations to become a specialized delicacy, made to tempt friendly birds and scare away mammals.

Non-YouTube mammals, atleast.

Sources: Tewksbury and Nabhan (2001),, YouTube


Posted by on June 5, 2012 in Natural History


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3 responses to “Burn Notice: Why Chilis Taste Hot

  1. Caddisfly

    July 6, 2012 at 12:11 pm

    I cut some jalepenos last night to make stuffed peppers and my hands still feel hot! All that capsaicin huh. Thank you for this article.

    • theglyptodon

      July 7, 2012 at 12:50 pm

      Hahaha, no worries. Sorry about your hand.


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