The sleep paradox: why do humans sleep so little when we need it so much?

"Aristotle argued that sleep is a necessary, natural suspension of consciousness that allows the body and soul to recover. This view fell out of fashion during the Age of Enlightenment in the late seventeenth century. The philosophers John Locke and David Hume, for example, thought that sleep hindered rationalism and the pursuit of knowledge. Hume lumped sleep together with fever and madness as an impediment to rational thought. Locke saw sleep as a regrettable, if unavoidable, disruption of God's desire for humankind to be rational and industrious."

"Modern science, meanwhile, has increasingly come to echo Aristotle. It provides a chorus of evidence about the importance of sleep for a host of crucial functions, including cognition, emotional regulation, immunity, metabolism and social bonding. Sleep is essential for cleansing the brain of metabolic waste, trimming synapses and maximizing the efficiency of cognitive processing."

"By studying sleep patterns across closely related species, he estimates that humans require roughly 9.5 hours of sleep per day to fulfil their basic biological needs. Yet, averaged across cultures, people get just under seven hours a day. Samson dubs this 2.5-hour discrepancy the "human sleep paradox" and makes it the central topic of his book, The Sleepless Ape."

Sleep is a natural suspension of consciousness that supports recovery of body and soul. Earlier views that treated sleep as an obstacle to rational thought later gave way to modern scientific evidence linking sleep to cognition, emotional regulation, immunity, metabolism, and social bonding. Sleep helps clear metabolic waste from the brain, trims synapses, and improves cognitive processing efficiency. A biological anthropologist asks why humans sleep so little despite these benefits. By comparing sleep patterns across closely related species, he estimates humans need about 9.5 hours daily for basic biological needs, while cultural averages show just under seven hours. This gap is framed as a “human sleep paradox,” central to explaining human short sleep through evolutionary selection pressures.

Read at Nature