"Continuous sleep is a modern habit, not an evolutionary constant, which helps explain why many of us still wake at 3 am and wonder if something's wrong. It might help to know that this is a deeply human experience.
For most of human history, a continuous eight-hour snooze was not the norm. Instead, people commonly slept in two shifts each night, often called a "first sleep" and "second sleep."
Interesting read:
"Humans Used to Sleep Twice Each Night. Here's Why It Vanished."
https://www.sciencealert.com/humans-used-to-sleep-twice-each-night-heres-why-it-vanished
#ScienceAlert #Sleep #HumanBehaviour