Freeing Animals From Our Evolutionary Traps


James Snyder noticed one day that a frog had climbed onto a tree in his backyard in southern Florida and swallowed one of his Christmas lights. He snapped this eerie photo in which the light glows through the frog’s stomach, like a herpetological holiday ornament.

This frog’s behavior seems weirdly stupid. But there’s actually a wisdom of sorts in swallowing a Christmas light–if you’re a Cuban tree frog, that is. For thousands of years, the only glows  your ancestors ever saw on a tree came from luminescent insects. If they responded to a little glow by attacking, they got a meal. They were more likely to survive and have baby frogs. The frogs that didn’t respond? Some of them may have done just fine. But others may have gone hungry. The males might have struggled to attract a mate; the females might have laid small eggs that failed to develop.

Natural selection laid down this response in Cuban tree frogs, in other words. Christmas lights have only recently come into their lives, and natural selection has shown no sign yet of striking the “attack glowing light” behavior off the menu.

Snyder’s glowing frog is one of the prettiest examples of a surprisingly common thing that happens when animals come into contact with humans. We have altered the environment in a vast number of ways, both small and large. And when animals try to read the cues from our human environment, they can get tricked. They can end up doing something that kills them, loses them the opportunity to reproduce, or simply wastes their time. Scientists call these situations evolutionary traps.

Written By: Carl Zimmer
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  1. How long did it take for the little frog to realize the light wasn’t digestible?
    Shorter than a fundie drops the god delusion I hope.

  2. Hopefully this type frog can regurgitate the bulb. Some frogs ( I forget the species ) can regurgitate their entire stomach and clan out the contents with their forelegs.

  3. This is rather like the evolution of theists who have managed to swallow a whole load of bullshit by thinking it gives them better inclusive fitness by supernatural protection. It may be a few millenia before they reaslie they’ve been the victim of a plausible but rather unsophisticated fraud.

  4. The question is: who is crazier? A frog eating a light bulb or a human hanging a light bulb in a tree?

  5. I guess this is one drawback to these new Fluorescent/LED Xmas lights… Since they generate almost no heat, the frog can eat it without burning itself. This wouldn’t have happened back in the days when all Xmas lights were incandescent bulbs. Those gave off so much heat that the frog would simply have not been able to get near it. So I guess it’s an evolutionary trap in more than one way 😉

  6. In reply to #8 by QuestioningKat:

    oooo! Tanya and Sheila…do we have newbie females on RDnet? Welcome ladies!

    Yep you have! Thanks and Hi!

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