Darwinian Dogma Doubted: Cave Fish Go Blind on Purpose

Contrary to previous belief, blind cave fish have the genes to build eyes but turn them off during development, reports Science Now. 

When a body part is no longer needed, scientists usually assume that mutations accumulate in the genes controlling the structure, eventually preventing it from working or being made.  “That was the dogma,” says Stephen Ekker of the University of Minnesota, Twin Cities.  But because the cave fish eyes are actively killed, natural selection is probably doing its thing, says Jeffery.  And that, he adds, might come as a surprise even to Darwin, who thought the cave fishes’ loss of sight might be an exception to the rules of natural selection.  The next step, of course, will be to figure out what the fish gain by losing their sight.

So it’s not simply an issue of “use it or lose it,” the article states; “new research suggests that for some cave-dwelling fishes, blindness results from the careful coordination of gene expression, not simply from lack of use.”
    Science News also reported this story, describing how the researchers could induce blindness in sighted fish by controlling the expression of a gene, and could partially restore sight in blind fish with different gene regulation.  The article ends, “Because the genes orchestrate both mouth and eye development, the blind fish may have lost their eyes as t hey gained a more effective mouth—a useful feature for catching food in the dark.”

Creationists have argued that natural selection eliminates things, rather than constructing them, so this is no surprise.  What is surprising is that the eyes did not merely degenerate through disuse, and that the response could have occurred quickly through changes in the regulation of one gene during development.  Maybe there is a functional reason why this gene is being switched off in the darkness of the cave environment.  Maybe with eyes not in the way, it helps enhance the other senses the fish will need when sight is not possible.  Whatever the reason, natural selection cannot be credited with creating new function, because both eyes and mouths already functioned well.