Chronotypes: Siffre’s Study on Sleep Timing Variability

Chronotypes and the Biological Benefits of Variability in Sleep Timing

Walker discusses the concept of biphasic sleep, where some cultures, particularly hunter-gatherer tribes, have a sleep pattern that includes a longer sleep at night and a short nap or siesta during the day. These tribes also tend to go to sleep about 2 hours after sundown and wake up just before sunrise, with temperature being a strong predictor that forces them awake.

Huberman and Walker also explore the concept of midnight being the middle of the night, and how this varies depending on an individual’s chronotype. While some people, like Jocko Willink, are early risers who go to bed around 8 p.m. and wake up at 4 a.m., others may naturally get sleepy later and wake up later.

The variability in chronotypes is seen as a biological benefit, as it ensures that there are always some people awake at any given time, reducing the vulnerability of the collective. This injection of variability in sleep preferences is similar to how the circadian rhythm is not exactly 24 hours, allowing for entrainment to the changing light-dark cycles throughout the year.

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