If you’ve ever spent some time in the Caribbean, you might have noticed that humans are not the only organisms soaking up the sun. Anoles—diminutive little tree lizards—spend much of their day shuttling in and out of shade. But, according to a new study in Evolution led by assistant professor Martha Muñoz at Virginia Tech and Jhan Salazar at Universidad Icesi, this behavioral “thermoregulation” isn’t just affecting their body temperature. Surprisingly, it’s also slowing their evolution.