Charles L. Nunn

Department of Evolutionary Anthropology Duke Global Health Institute

Duke University

 

Sleep is essential to cognitive function and health in humans, yet the ultimate reasons for sleep – i.e., why sleep evolved – remain mysterious. We integrate findings from human sleep studies, the ethnographic record, and the ecology and evolution of sleep, including recent phylogenetic comparative studies of sleep architecture and arousability in primates and other mammals. Based on these comparisons, we show that sleep in great apes is a derived trait that has undergone substantial evolutionary change from other primates, and that further evolutionary change characterizes human sleep. We discuss how these changes provide important insights to the linkage between sleep, cognitive performance and human health. We also identify the vastly different ways that humans in the developed world sleep compared to our recent hominin ancestors, especially due to access to electrical lighting, but also through our use of separate bedrooms, soft beds, and cultural norms against daytime napping. These cultural changes and our evolutionary history have consequences for understanding sleep disorders, including insomnia, seasonal affective disorder, and circadian rhythm disorders. In conclusion, our research identifies phylogenetic comparisons as key to understanding human sleep in broad evolutionary perspective, especially when combined with the ethnographic record and recent experimental studies of sleep.