Although they’re known for laying eggs, some snakes and lizards give birth to live young just like mammals do. They supposedly do this to protect their offspring from cold climates. But that hypothesis couldn’t explain why some tropical lizards and snakes bear live young. Now, a study of one family of lizards, presented here on Saturday at Evolution 2013, the annual meeting of the American Society of Naturalists, the Society for the Study of Evolution, and the Society of Systematic Biologists, shows that tropical live-bearers hail from high elevations—where it can get cold—and suggests that this reproductive strategy in reptiles may often originate on tropical mountainsides. Leer más.