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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.
The manner in which the evolution of flightless birds or eyeless, cave-dwelling animals might have come about was a problem that Charles Darwin considered; his answer was that disuse would lead to the progressive reduction, or degeneration, of organs over time. We do not believe this is correct anymore, but many share Darwin's confusion, even today. Stephen Jay Gould, in his 2002 magnum opus, The Structure of Evolutionary Theory, listed the three things that his readers found most confusing, as measured by the correspondence he received.
While all three are interesting questions, let's consider just the third, which Darwin failed to answer. Why should animals living in total darkness lose their eyes? It's a question that highlights the importance of developmental biology in explaining some evolutionary phenomena...and it's also an excellent way to introduce this new column, in which I'll regularly be discussing the evo-devo way of thinking.
