A chimpanzee hugs her newborn at Burgers' Zoo in Arnhem, Netherlands, in 2010. Over the course of his long career, primatologist Frans de Waal has become convinced that primates and other animals express emotions similar to human emotions. AFP/Getty Images hide caption
A chimpanzee hugs her newborn at Burgers' Zoo in Arnhem, Netherlands, in 2010. Over the course of his long career, primatologist Frans de Waal has become convinced that primates and other animals express emotions similar to human emotions. AFP/Getty Images hide caption
Cover detail from Zora and Langston, by Yuval Taylor W. W. Norton hide caption