I recently read an article about sleep patterns in animals, and it was fascinating to learn that some animals have bi-phasic sleep patterns, meaning they sleep in two phases instead of one long stretch like most humans. It got me wondering why these animals have evolved this way and what advantages it might give them.
In: Biology
I believe that humans are also bi phasic naturally. Until recently, humans would have a four hour sleep at sundown, then get up in the night and go out, visit their friends and so on, before returning for a second sleep. The invention of the light bulb changed those habits.
the most common version of this is called a “crepuscular” activity pattern, which means the animal is most active at dawn and dusk, and is inactive most of the day and middle of the night. That doesn’t mean they sleep during the entire inactive period, but they don’t tend to move around very much.
the main reason is that dawn and dusk provide enough light to see, but are also dark enough to avoid being seen by predators. Walk around outside at dusk and you’ll see what I mean. You lose your color vision in dim light, and it becomes very difficult to see anything that isn’t moving. This provides some protection to prey species (and unless you’re the apex predator, you’re a prey species, even if you’re a carnivore).
Spend enough time sleeping outdoors without lights, and watch your sleep pattern shift to biphasic.
[https://en.wikipedia.org/wiki/Polyphasic_sleep#Ekirch’s_analysis_of_biphasic_sleep_in_the_pre-industrial_era](https://en.wikipedia.org/wiki/Polyphasic_sleep#Ekirch’s_analysis_of_biphasic_sleep_in_the_pre-industrial_era)
Source: long distance hiker
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