As our understanding of gender evolves, it might be helpful to think about the topic by expanding beyond humans to include all primates. Frans de Waal is professor emeritus of primate behavior at Emory University and the former director of the Living Links Center at the Yerkes National Primate Research Center. He joins host Krys Boyd to discuss challenges to what’s understood about masculinity and femininity and the limitations of gender binary thinking. His book is “Different: Gender Through the Eyes of a Primatologist.”