Why Did Zebras Get Their Stripes?

Why do zebras have stripes?  It’s a question many kids have asked their parents, and one that many scientists have tried to answer.  Now researchers say they’ve solved the puzzle, and it has to do with . . . flies.

Awful, blood-sucking horseflies, to be precise.  The researchers contend that the patterns of stripes reflect light in a way that makes zebras unattractive to flies.  They conclude that the coats of black and brown horses, poor devils, reflect light in a horizontal way that horseflies love, whereas the coats of white horses don’t reflect light in that way and, as a result, white horses are less troubled by painful fly bites.  When stripes were added, the researchers found, even fewer flies were attracted.  Hence, they believe that stripes evolved to keep flies away.

Color me skeptical.  Much as it sucks to be bitten by blood-sucking flies — and it does — it’s not life-threatening and wouldn’t seem to be a sufficient cause for a significant evolutionary detour.  If it were, we wouldn’t be seeing black and brown horses romping through the pastures of Ohio, and elsewhere.  As I understand evolution, the process of natural selection works only if a genetic variation makes the individual with the variation more likely to survive and reproduce.  A variation that allows you to be more successful at avoiding non-life-threatening fly bites wouldn’t seem to fall into that category.

On the other hand, it could be that lady zebras long ago decided that black-coated males who were covered with biting flies were less attractive potential mates than those cool, laid-back striped dudes over by the watering hole who weren’t frantically twitching their tails at swarms of horseflies.  Or, alternatively, the black-coated lady zebras tormented by blood-sucking flies were less likely to be in a receptive reproductive mood than their serene, striped counterparts.

 

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