I Can't Fly! Birds Lost Their Aerial Abilities Multiple Times

Ostriches, kiwis, emus—these birds always look out of place, bound to the land while their feathered cousins take to the sky. It's easy to imagine that flightlessness evolved only once, and that bird species then split into several species; indeed, most scientists figured that was what happened. But according to a study led by John Harshman of the Field Museum of Natural History in Chicago, that's not so: Birds lost the ability to fly at least three times. Harshman's team began to poke holes in the common ancestor hypothesis by examining DNA from the different birds to see how they were related. The researchers found that emus and kiwis were actually more closely related to a ground-dwelling but flight-capable bird called the tinamous, which lives in the Americas, than they were to ostriches. Previously, the standard explanation for the different kinds of flightless bird centered on continental drift: The common ...