The human sleep paradox is the result of our evolutionary history

To learn about how ancient humans slept, anthropologists study contemporary non-industrial societies, such as the Hadza hunter-gatherers of Tanzania and various groups in Madagascar, Guatemala, and elsewhere. Sleep across all three groups averages around 5.7 - 7.1 hours, which is much less than primates.

Evolutionary anthropologist David Samson thinks the evolution of human sleep is a story about safety in numbers when humans began sleeping on the ground and napping often.