Monkeys and apes are unable to learn new vocalizations, and for decades it has been widely believed that this inability results from limitations of their vocal anatomy: larynx, tongue and lips. But an international team of scientists has now looked inside monkeys’ vocal tracts with x-rays, and found them to be much more flexible than thought before. The study indicates that the limitations that keep nonhuman primates from speaking are in their brains, rather than their vocal anatomy.