Where Human Sleep Went Wrong

Sleep, an essential aspect of human functioning, has evolved uniquely among primates. Evolutionary anthropologist David Samson, author of The Sleepless Ape, delves into the sleep patterns of humans and other primates in his book. Living among the Hadza tribe in Tanzania, Samson noticed their fragmented, short sleep duration, and low efficiency, which was partly due to nighttime activities like storytelling and dancing.

Despite this, the Hadza consistently reported high satisfaction with their sleep, challenging the belief that hunter-gatherer sleep must be long and deep.

Samson's research led to the concept of the "sleep paradox": humans sleep fewer total hours than any other ape, yet we are the most evolutionarily successful primates. This mystery prompted Samson to explore the origins of what he calls the "lie-down-and-die" model of Western sleep. Early humans, after descending from the trees around 1.8 million years ago, began constructing physical microhabitats like acacia shelters to regulate temperature and create more comfortable sleep environments.

This adaptation, coupled with mastery of fire and social living conditions, formed a novel sleep ecology, or "physical sleep exophenotype."

This exophenotype led to significant evolutionary changes in sleep patterns, resulting in humans having more REM sleep relative to their short duration. REM sleep functions as a nightly emotional reset, helping to process memories without retaining excessive emotional charge. Consequently, sleep deprivation impacts cognitive functions and overall well-being.

Despite knowing the importance of sleep, humans often struggle with insomnia, a phenomenon Samson attributes to our unique evolutionary sleep patterns and the effects of trauma on sleep quality.