Religion Drives Evolution

This morning, I was driving up Torrey Pines mesa, blowing past some Prius that was gamely working its way up the incline when I noticed it had one of those little “Darwin Fish” badges.  You’ve seen them, they look like the “Jesus Fish” badges except they have little legs.  Clever.   Anyway, while leaving him in my fossil-fueled dust, it reminded me of a story that I’d been meaning to post about for a bit.

In a recent issue of “Biology Letters” there was a paper led by a group at Texas A&M that described the changes in a subpopulation of the Atlantic molly (a small fish) that lives in a cave in Mexico.   It turns out that for centuries, the Zoque people take a spring pilgrimage to the cave to pray for a good rainy season. As part of the ritual, they release into the cave’s waters a paste made of leaves, limes and the roots of the barbasco plant.  As it turns out, barbasco root is toxic to fish.  So a little while after they release the paste, dead fish start appearing on the water’s surface.  The fish are seen as a blessing from their god for their devotion.

Zoque Ceremony

What the Texas A&M team did was collect mollies from the cave and compare them to mollies collected from different areas.  When the fish were exposed to the barbasco root toxin, the sacred cave fish had a much higher survival rate than the control fish.   The cave-fish had been selectively pressured such that the ones that could endure the toxin and reproduce survived and the ones that couldn’t became dinner.                                                                                                              


Now, this sort of selective adaptation can be created in the lab for microbes and things that have short generational cycles, but it’s been harder to demonstrate for bigger, longer-lived, and more complex vertebrate organisms like fish.  But here, there was an isolated fish population and a selective pressure that had been going on long before the Europeans arrived in the New World.

See? It all works out

Sadly, a couple of years ago, the Mexican government made the Zoque people halt their ceremony and now they only get to perform a “faux” one (without the toxic root) each spring.  If that ban stays in place, we’ll have to check back in another 500 years or so to see if there’s been any drift in the population.

17 thoughts on “Religion Drives Evolution

  1. Fascinating! We see evolution in action in our Microbiology lab all the time. Organisms adapting and becoming resistant to antibiotics.
    We have now identified a bacteria that when exposed to antibiotics developes a gene which it sends out to other bacteria, letting them become resistant without even being exposed!
    Great stuff…well, horrifying, but interesting!
    I love the godlovesevolution fish!

  2. This reminds me of the “rattlesnake roundup” that gets held every year in Texas (and in other places). Folks typically find the snakes by listening for the rattle. As a result, they are selectively breeding quieter rattlesnakes, which means that they are breeding deadlier snakes.

    Who says that evolution has no sense of humor?

  3. I had a Darwin fish on my old Camry: you wouldn’t believe the amount of hate it would draw in the Midwest. I had cars tailgate and lean on their horns at me, a redneck throw a beer can at the fish, and a carload of teenagers scream “JESUS SAVES, DARWIN SUCKS!” as they blasted past me. A Christian “friend” took me aside and said my fish was offensive to her religion, and I snarled back that her religion offended my fish. I was almost relieved when it finally fell off in the Super Tidal Wave Car Wash, though the hectoring became yet another reason why I decided to get out of Middle America.

    I think Darwin had the last laugh, however. The human genome project found traces of worm, fish, and rodent DNA among our primate genes. So we have something in common with those little fish in the cave. Who knows, maybe we’ll slowly adapt to the toxins in our own environment. Which might not be a good thing for us in the long run.

    • I have a Flying Spaghetti Monster on my car. I am surprised it hasn’t caused more of a reaction….but I guess it’s not as obvious as a Darwin fish.

      One of my favorite bumper stickers was “No, I didn’t make it to church this week. I was too busy studying witchcraft and being a lesbain.”

      • I don’t think anyone in rural Minnesota knows what a FSM is, so you’d be safe there. But if you said the L word out there, people would freak. The W word, and they’d start gathering firewood.

    • Wow — that’s pretty scary, HG. When I was looking for images for this post, there were a TON of ones that had a big Jesus fish eating a little Darwin fish. I wonder if Jesus would really want to be seen as devouring part of His Creation??

      • I personally take credit for all the people in my neighborhood who put the Jesus-fish-eating-the-Darwin-fish plate on their cars. They took notice. Which was sort of good. But I don’t think they connected evolution to their idea of God’s plan.

        There was a huge Baptist church in our town that tried to get the local school district to teach Intelligent Design. Happily it never got beyond the screaming and shouting point, but the science teachers at the high school all threatened to quit if they were told to teach what they said was anti-science. I was proud of them, but also a little scared that there were so many people who would support that sort of thinking.

  4. I think it’s sad that we made them stop that part of the ritual. What right do we have? It’s not as if we don’t pour out many more toxins into our own environment every day. Sigh.

  5. I say it all the time. God is smart enough to invent a science where stuff evolves. That does not mean that man was once ape. Man was once slightly smaller man with hunched back, longer arms, and sloped forehead. Who knows what we were before that.

  6. Full disclosure – I have a Jesus fish on my car, and while I appreciate the wit of the Darwin fish, I do find it offensive. I think if you know the history of the “Jesus fish” (or ichthus) you may understand some of the frustration directed towards the Darwin fish. In early Roman times Christians were persecuted for their beliefs, as they still are in certain parts of the world today. The fish symbol became a code to fellow believers – a reference to Jesus’ teaching to be “fishers of men”. Ichthus is also Greek for fish and, in Greek, an acrostic for “Jesus Christ, God’s son, savior”. For many Christians parodying the ichthus as the Darwin fish mocks Christian beliefs and ignores the persecution of Christians for those beliefs. I don’t agree with bullying or violence toward someone with a different view, but neither do I agree with belittling someone else’s beliefs. True tolerance can only be achieved when we stop putting down those who don’t agree with us and try to understand their viewpoint.

    • J — good points, and I remember all my Catholic school teaching about how the fish came to be a symbol for Christ. To me, the Darwin-fish is meant to be more ironic than mean-spirited, but it’s clear from some of the comments above that people take it REALLY seriously.

      I do think though that the big Jesus-fish eating the little Darwin-fish is pretty mean-spirited. When I was searching for images for this post, I found a LOT more of those than ones in which they were co-existing. Which is sort of sad.

      • That’s what I love about the Jesus fish showing some love with the Darwin fish.

        My FSM is definitely ironic. And I wouldn’t want anyone to think I was belittling their beliefs. Just sharing my own, as they do.

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