Despite sleep’s critical role in maintaining health and cognitive function, humans sleep less than any other primate. “The Sleepless Ape” reveals the reasons for this evolutionary paradox, showing how our unique sleep patterns evolved when our ancestors left the safety of the forest for more dangerous ground, which led them to form more secure, social sleeping arrangements. As a result, early humans developed shorter, deeper, and more flexible sleep patterns that provided survival advantages and freed more time for crucial activities such as toolmaking, social interaction, and migration.