The Sleepless Ape: The Story of Sleep in Human Evolution David R. Samson Princeton Univ. Press (2026) Sleep deprivation disrupts memory: here’s why For millennia, philosophers have argued over why humans sleep and dream. In his fourth-century- bc treatise On Sleep and Sleeplessness , the philosopher 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. The essayist Jonathan Crary put this view more succinctly — “sleeping is for losers” — when he wrote about how sleep is often devalued in modern society 1 .…