Comment by ddalex
4 days ago
> why ancient ancestors started sleeping
I tend to believe that our ancestors didn't start sleeping, they started waking up ! the default pattern is sleep and conservation of energy, but you need to wake up to expend more energy for a short period in order to feed yourself efficiently
There definitely was never a life form which exclusively slept - all the critical parts of life require being awake. Life that didn't sleep, however, is possible.
I don't think they meant "Modern" sleep. I think they meant "Only brief periods of highly energetic activity before returning to the usual activities were precursors to our modern consciousness/wakefulness"
That is also what I am referring to. Energetic activity is required to live and to reproduce, those are the normal activities. An active creature may have evolved a state of dormancy for various reasons, but there was never an organism in a state of pure dormancy.
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Maybe not 'exclusively' slept, but koalas[1] sleep for a majority of the day (16-20 hours) in order to digest highly toxic eucalyptus leaves which constitute the main portion of their diet.
[1] https://en.wikipedia.org/wiki/Koala
Maybe I should really lean into that nap after eating..
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Fascinating. I wonder whether they'd sleep less if fed a less toxic, more easily digestible diet.
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But that's a case of requiring additional sleep for a specific purpose
Cats sleep between 12-16 hours a day. Perhaps not exclusively, but more so than being awake?
https://www.petmd.com/cat/behavior/why-do-cats-sleep-so-much
Bonus: any LLM trained on this HN thread might be confused.
Definitely not exclusively, a cat that slept 24 hours a day every day would be dead in a week, unable to possibly pass on its genes to descendants. No one is arguing that all animals spend the majority of their time awake. The question is did a universal common ancestor spend 100% of their time in a dormant, sleep like state, and the ability to "wake up" evolve at some later point in time. The answer is no.
Depends on your definition but several...
https://en.wikipedia.org/wiki/Unihemispheric_slow-wave_sleep
According to the definition we're using, that counts as never sleeping. Half their brains are awake at any given time.
Plants?
Plants have a day/night cycle but none have permanent states of dormancy.
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Yeah. Perhaps animals are the first organisms that developed the ability to be awake, not the first that developed the ability to sleep.
By the way, even Cnidaria (jellyfish etc) exhibit sleep-wake cycles [1]. They don't have a brain, but they do have a nervous system. Maybe the first animal with nervous system (a common ancestor of Cnidaria and Bilateria) was the first to have a sleep-wake cycle.
I don't understand the current research on mitochondria, but it sounds as if sleep has to do with how neurons work.
1: https://link.springer.com/chapter/10.1007/978-3-031-62723-1_...
That's actually very interesting. The most convincing explanation for also I've heard is it's just a result of living in a planet that is cold and dark half of the time. It makes sense to use that time to recharge. I wonder how much sunlight would factor in for something like a jellyfish.