Ancient science, modern discoveries, & animals that sleep with one eye open
Just like the last time I was pregnant, I've been sleeping a stupendous amount. If history repeats, things will improve during the second trimester, but my complete inability to function in the evenings if I haven't taken a nap reminded me of various sleep habits I'd read about, so I thought I'd compile them here and maybe integrate them into a story to commemorate my second pregnancy heh.
- Most primates do not build even temporary sleeping nests, but all the great apes do. Most primates are diurnal; fragmented sleeping patterns (i.e. going to bed, waking up for awhile, and then going back to bed) are probably due to things like light, food, and external constraints imposed by predators.
- Collective sleeping is a distinctive feature of Māori cultural customs; it's a central component of ceremonial gatherings for community members to sleep together in ancestral meeting-houses. I imagine this is similar to how a big American family might get together at Grandma's house and everyone sleeps in sleeping bags in the living room because there aren't enough guest rooms.
- Egyptians are some of the first people we know of to practice sleep medicine. Medical papyri mention various sleep disorders, and we know they used poppy seeds (opium) to treat insomnia. Egyptians also used sleep as a method of healing; they even had special sleep temples designed for dream incubation.
- Many Muslims change their sleep habits during Ramadan fasting; there are also voluntary night time prayers that some people participate in. There are also vows meant to be made at night (or certain times of night mentioned in the Qurʾān.
- It wasn't until the 1980s (!) that scientists established that sleep was a function of circadian rhythms. Biological rhythms weren't really a known concept until the late 60s, and REM sleep wasn't really known until the 50s. Most of our modern ideas about sleep come courtesy of a broke graduate student named Eugene Aserinsky.
As with many cultures from around the world, Early Niger-Congo peoples used mats for sleeping and preparing food. Although I'm shaky on how exactly the mats helped with food preparation (does anyone know?), these constituted their primary woven items for everyday use, along with baskets for various purposes. As far as I can tell this is one of the earliest types of beds used by humans; we have evidence that very early humans constructed sleeping mats from local plants, including some with insecticidal properties.
There is, perhaps unsurprisingly, a great deal of scholarly debate about "natural" human sleep patterns. For one thing, modern hunter-gatherers are probably a relatively poor proxy for ancient communities. For another, sleep is often grounded in social norms and cues rather than purely being about physiological needs. That said, it's definitely worth noting that sleep habits among humans really do seem to be variable depending on a lot of factors, just as with various primate species. Factors like heat, the availability of light and work, hunger, etc impact sleep patterns, and diurnal sleep patterns are certainly not uncommon among various human populations. That said, there's an argument to be made that diurnal sleep habits in pre-Industrial humans are a result of illness, anxiety, and environmental problems, and therefore disordered.
The closest thing to a truly nocturnal society I was able to find was the Kingdom of Ormus, a maritime kingdom with its capital on a salty, barren island rife with violent sandstorms. The people shopped and socialized almost exclusively during the night. 17th century Portuguese engravings claimed that the people of Ormus slept in wooden coffins filled with water to fight the heat.
Although most animals sleep with their whole brain and body, some animals, like crocodiles, manatees and frigatebirds, can sleep unihemispherically, which is to say that one cerebral hemisphere sleeps while the other is awake. In fact, cetaceans (dolphins & whales) sleep only unihemispherically, while seals and birds mix unihemispheric sleep with bihemispheric and rapid eye movement sleep events. Although it seems intuitive that birds who fly for ten days in a row might sleep unihemispherically while in flight, they mostly just don't sleep... and when they do, it tends to be when they're soaring or gliding.
📗 If you found this interesting, you may also enjoy the previous edition about beds.
💚 If you learned something from this overview, consider forwarding it to a friend and encouraging them to sign up for more overviews of my research into obscure history and science.
😴 Do you have a favorite bit of trivia about sleep? Please reach out — I'd love to hear about it, either via email or in a comment where other readers can see.
Note: There are a couple of affiliate links & codes scattered around, but these always come from links I was already recommending and usually I share them because they benefit you too (i.e. getting you extra time on trials).
Check out one of these related posts
Cloth records, syllabic scripts, and bone calendars.
Antiseptic poop, agricultural poop, & the surprising value of eating poop.
Quick facts about historical cleaning methods from around the world, from lotus leaves to bronze knives.