The evolutionary rationale for why various creatures are they way they are can be tricky to figure out. Sometimes there’s actually no good reason—simply that a trait which once had a purpose has not been weeded out as times change because it’s relatively innocuous (like embryonic tails and wisdom teeth). Because when it comes to evolutionary adaptation, the maxim is “if it ain’t broke, don’t fix it.” But other times there is indeed an important function at play that’s not immediately apparent to us mere mortals.
One quizzical feature that has left scientists scratching their heads for eons: zebra stripes. Other than their appeal for zoo-goers and nature film fans, it’s been unclear what purpose the black designs serve. Some conjectured they are an optical illusion to confuse predators; others that they are decoration for mating. But evidence is piling up that the stripes actually evolved as a design-based insect repellent.
How did scientists figure out this little factoid? A clever bit of deduction. Researchers mapped out different species of the horse family to see what traits corresponded with which terrain. And they realized that the species with stripes showed up in areas plagued by biting flies, like the great plains of Africa. They factored in previous research indicating that flies don’t like to land on striped surfaces—for reasons still unclear—and voila, a new compelling theory. Unfortunately not all insects share this aversion, otherwise your striped t-shirt would be a must for summer days by the river.
Image: commons.wikimedia.org.
