It's Not the Jet Lag

(today.com image)

Most of us have had the experience of sleeping fitfully the first night in a strange bed but more easily in the nights thereafter. There's now a scientific explanation: [bold added]

from previous work conducted on birds and dolphins...these animals put half of their brains to sleep at a time so that they can rest while remaining vigilant enough to avoid predators....[Humans'] first-night effect is a mechanism that has evolved to function as something of a neurological nightwatchman: to wake people up when they hear noises when sleeping in an unfamiliar environment, even one with a comfy king-size bed, jacuzzi, deluxe minibar and a distinct lack of predators.

The left side of our brain doesn't sleep in an unfamiliar environment because it's watching for predators.

Our caveman ancestors had no use for high coil-counts and sleep numbers. A trusty spear, on the other hand, meant nighttime bliss.