It's a commonly held belief that before artificial lighting, human sleep was 'naturally' divided into two distinct periods, but how true is that?

On dry nights, the San hunter-gatherers of Namibia often sleep under the stars. They have no electric lights or new Netflix releases keeping them awake. Yet when they rise in the morning, they haven’t ...

A new study analyzed the sleep patterns of jellyfish and sea anemones and found they share some sleep traits with humans. The research could provide insight into the origins and function of sleep.

Sleep appears to have developed much earlier in animal evolution than previously assumed, according to new studies on two brainless marine creatures. A study of the upside-down jellyfish Cassiopea ...

For hundreds of years, night didn't mean a long sleep. Long before electric lights lit up homes and streets, people lived ...