[worksonmymach]

Why is it not a survival advantage? Probably because we didn't work 18 hour days, the extra wakeness would just be used for rest.

Night shifts that anyone can do are still needed if you need tribal watchers, and normal 8hr sleeping people can wake upnand fight when needed.

In terms of the gene, I am suprised how rare it is (90 families?) given I have met someone who needs only 4hr sleep.

Another point is less sleep doesn't mean you can do 2 more hours work a day. That is another vector: how much work per day (physical, mental) can be done.

[hgomersall]

There's a plausible hypothesis that sleep is the thing that evolved precisely to stop us doing things for any more time than is strictly necessary. That is, sleeping is safe.

[jlpom]

I don’t think any serious biologists agree with it. There is a hard physiological need to repair cellular damage from metabolism, UV (this a big deal in unicellular species), etc. If this theory was correct, and it is possible to do it entirely while awake, there would be species (apex predators in particular) that would have evolved without the need for it, like everything that is not a hard requirement. But this is not the case.

[hgomersall]

There must far more to it than that. As soon as sleep is a thing, it can be optimised for different goals. Since animals have widely varying sleep requirements, there's clearly some evolutionary factor that influences sleep length.

That is, though sleep might have physiological requirements, it doesn't mean that the amount of sleep is not influenced by non physiological effects.

I'm constantly amazed by the ability of biologists to be amazed by the reach and ingenuity of evolution.

[grues-dinner]

Yes, but evolution didn't account for the need for those TPS reports to be ready by tomorrow morning and Bob over there is already 48 hours into his shift (don't worry he's on salary, the overtime is free).

[dotancohen]

Only 90 medically identified families. The condition is probably far more likely than just those medically identified. And people typically do not mention abnormalities that positively affect them to their doctors.

[toenail]

> Why is it not a survival advantage?

Because you're more likely to hurt yourself while doing anything in the dark?

[Barrin92]

The primary reason is that calories used to be a very valuable commodity to come by and predators expend a lot of them when they're hunting or exploring, which includes us humans. Also the reason cats nap a lot.

[JumpCrisscross]

> Why is it not a survival advantage?

“All organisms occupy a niche, and the better adapted to that niche, the more ‘fit’ and the more likely that organism will reproduce, passing on the characteristics that fit that particular niche. While we may simplistically think of each organism occupying a single niche, realistically nearly all occupy at least two. Daytime and nighttime are different and distinct niches, creating an evolutionary push and pull that would make a perfect ‘fit’ impossible. Evolutionarily, being forced to evolve into two separate niches at the same time forces an organism to develop structures and functions that fit neither fully” [1].

We didn’t evolve for a world with artificial lighting.

[1] https://pmc.ncbi.nlm.nih.gov/articles/PMC7120898/

[makeitdouble]

The night niche doesn't require artificial lighting though.

Moonlight can be enough to have a decent understanding of one's surroundings, and then there's more than vision to navigate and be active. We wouldn't need a full species level evolution to be good at night life.

[JumpCrisscross]

> Moonlight can be enough to have a decent understanding of one's surroundings, and then there's more than vision to navigate and be active

Decent for us. Great for our predators and prey.

> We wouldn't need a full species level evolution to be good at night life.

The point of the article, which granted is a hypothesis, is that the adaptations it would take to be good at night would make us no more than good during the day. Nature has clearly selected against jack of all trades species.

[makeitdouble]

On the day/night balance, I was looking at cats as an example of a species that sleeps in smaller chunks and splits activity all around night and day.

Reading the article I thought there should be more weight given to behaviors different from sleep to adapt to the other niche, and also that being perfectly adapted to a niche doesn't sound like a benefit in the first place. My understanding is that most species have an evolution process slow enough that they never completely fit a niche but also have enough versatility to move around.

I'm thinking dogs, bears, crows, racoons, migratory birds etc. where adaptation happens, but not to a degree they can't move out from their niche.

[JumpCrisscross]

> I was looking at cats as an example of a species that sleeps in smaller chunks and splits activity all around night and day

Cats are crepuscular. The niche hypothesis predicts they'd sleep most of the day and night.

> not to a degree they can't move out from their niche

No animal I know of can't survive outside its time niche.