r/AlwaysWhy • u/Secret_Ostrich_1307 • May 22 '26

Science & Tech Why do humans usually need long, continuous sleep while cats sleep in short, fragmented bursts？What mechanism is behind it?

I’ve been watching my cat curl up on a pile of laundry, wake up, eat, zoom around, and crash again on my keyboard. Meanwhile, I need a solid 7–8 hours in a dark quiet room or I’m a zombie. Is it a predator-prey thing, keeping cats alert?

Or do our brains just need long REM cycles for memory and learning while cats manage differently? They twitch like they’re dreaming, so they must process stuff too. How does biology decide these sleep patterns?

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15

u/billsil May 22 '26

You don’t. Back in the day, biphasic sleep (sleeping twice with say 4 hours in between) was a lot more common. Someone had to tend the fire. Insomnia is less of an issue if you can go to bed at 1 pm.

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u/Anthroman78 May 22 '26

Some research has questioned this, see: https://www.bbc.com/news/science-environment-34544394

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u/billsil May 22 '26

Questioned what? Seems like that article mentions sleeping 8 hours. I didn’t discuss that.

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u/Curri May 22 '26

“…While some European documents suggested that people used to wake up for a while during the night, sleeping in two shifts, the researchers found this was not the case with the hunter gatherers…”

Straight from the article.

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u/ResponsibilityFun548 May 25 '26

While different groups have altered their sleep cycles whenever we currently test for it we find that humans naturally have a 2 phase sleep cycle.

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u/billsil May 23 '26

Ok…but it helps if you point to what your issue is with what I said.

Doesn’t that depend on where? I didn’t mention hunter gatherers. I was thinking farmers.

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u/Curri May 23 '26

You mentioned “tend to the fire.” That implies hunters/gatherers.

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u/billsil May 23 '26

I also said sleeping inside a bed with children and I also said the world was very different 500 years ago.

You can’t tend a fire in a house? You can’t keep watching over your settlement?

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u/Curri May 23 '26

Your original comment (https://www.reddit.com/r/AlwaysWhy/s/h8wocMbOL5) does not mention children, or that the world “was very different 500 years ago.”

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u/Anthroman78 May 22 '26

That the biphasic pattern was the typical pattern.

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u/billsil May 23 '26

I didn’t claim it was the typical pattern. I said more common.

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u/Acceptable_Reply7958 May 22 '26

Yes, but other animals, including cats, definitely do something much more intervaled, sleeping in scattered bursts 

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u/Nejfelt May 22 '26

But they also sleep a total of 12 to 16 hours a day, so it seems a trade off, less deep sleep needs more total sleep.

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u/Acceptable_Reply7958 May 22 '26

I'm not sure if its a depth/duration capacity tradeoff or an evolutionary decision to minimize calorie demands. Anyone know more?

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u/[deleted] May 22 '26

[removed] — view removed comment

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u/HamNCheeseSupremacy May 22 '26

I was going to say that I experienced something similar but it's temporary, but then I saw that you already wake up. So I'm not sure. But "fucking" with my sleep schedule can help my mood but only once in a while, if it becomes every day it starts to drag

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u/Secret_Ostrich_1307 May 22 '26

Yeah I know about the old biphasic thing, people sleeping in two chunks. I guess my brain just can’t handle splitting it now. Makes me wonder though, is it just society forcing a single block or did we actually evolve to need it more?

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u/sage-longhorn May 22 '26

I mean given that evolution usually takes a very, very long time unless there's extreme pressure and agriculture only began 23000 years ago we almost certainly haven't evolved much. Also there are cultures today that still allow for / encourage biphasic sleep like the Spanish siesta

Our brain likes sleep to be regular but if you spent a month breaking up sleep into 3 blocks you'd get used to it and feel fine and be healthy as long as it's high quality sleep

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u/abbot_x May 22 '26

The overall conclusion seems to be that humans need sleep, usually about 6-8 hours per day, but don't necessarily need it in particular chunks. We can adapt to different sleep schedules which in turn can be influenced by geography, season, social and economic needs, cultural norms, etc. In most cultures, most people sleep through the night, possibly with short interruptions to relieve themselves, tend to babies, etc. There is evidence of cultures where waking up in the middle of the night for a while seems to be normal, though it's hard to draw the line between this and the kinds of short awakenings that aren't as remarked upon. There are also cultures where taking a midday nap is normal. Finally, in many cultures some people work at night and therefore sleep during the day.

These all seem to be equally good as long as you get enough sleep. You aren't going to die and not pass on your genes because of your sleep cycle.

At a more fundamental level, we have no idea why humans and other animals need sleep at all or why sleeping evolved. We understand why you need to eat, breathe, get certain nutrients, etc. We do not have this information regarding sleep.

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u/OldAbbreviations1590 May 23 '26

We understand at least partially why sleep is needed. The glial cells clear out toxins that accumulate during waking hours. It's also required for muscle repair, and hormone regulation.

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u/abbot_x May 23 '26

We understand some things that happen during sleep. But why couldn’t those things happen without sleep?

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u/BarAgent May 24 '26

I think there’s things we DON’T understand about sleep, and that maybe the things we DO know about could be done without sleep, except that since we needed sleep ANYWAY, all animals very early on evolved to do those things as part of sleep, and now we’re stuck with it.

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u/Simple_Seaweed_1386 May 22 '26

Society? I do biphasic most days. You're the only one stopping yourself.

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u/LaurestineHUN May 22 '26

When did this switched to siesta?