Lamarckianism

I like to use the example of the blind cave fish to test whether my students still harbor Lamarckian notions about evolution or if they have really caught on to the idea of natural selection. It's a good example because the Lamarckian explanation is so tempting. It just seems so logical that the cave fish lost their eyes because in total darkness they just don't need them anymore.

I bring this topic up again after mentioning it last week regarding wisdom teeth. Then yesterday reading an excellent book called simply Mutants, about all the things that can go wrong in a developing human embryo, I stumbled across this line (italics mine):

...But delightful as it may be to look at, red hair is not good for anything at all (i.e., has no adaptive survival value in any environment in which humans live ). MC1R (for simplicity's sake, the gene that causes dark hair when it functions "properly," red hair when it doesn't) may simply be a gene that is decaying because it is no longer needed, rather as eyes decay in blind cave-fish.

Now, I'm reasonably certain that the author is a hundred times more knowledgeable about biology, genetics and evolution, than I am, and yet either through carelessness or brutal editing, has issued a Lamarckian explanation for an evolutionary phenomenon. It's an otherwise fabulous book.

I started doubting myself, maybe I don't know as much as I thought I did. Maybe decay is the answer and I just haven't thought it through thoroughly enough to see how it works. But alas, serendipitously, I found PZ Myers' article in Seed Magazine on the very topic of HOW THE CAVEFISH LOST ITS EYES.

The Mexican blind cavefish raises the challenging evolutionary question: Does disuse lead to degeneration or disappearance of a feature? Here, an answer Darwin would have loved.

I certainly can't do the article justice by summarizing, so I'll leave you to go and read it for yourself. It's relatively short and sweet. I'll give you a hint about the ending - it's not Lamarck.