You’re really off about that. Our night vision is actually pretty good, especially if you’ve used it for every night of your life. Fire’s clearly been with us for long enough to be a factor, in addition.
I’m against the hypothesis though, if only for the fact that energy levels peak shortly after waking up - “why we sleep” discusses this a little.
That book also suggests the variety of sleep patterns exists for evolutionary reasons. Ie we are social creatures. Having a multitude of waking/restful cycles in a group kept our ancestors protected with a nearly round the clock group of protectors - who evers sleep cycle woke them up when ever.
It isn't good enough to see what's going on when it's actually pitch black, which it is most of the time at night.
> Fire
Lighting a fire at night in the place where you're having sex seems like a pretty good way to get discovered.
> Having a multitude of waking/restful cycles in a group kept our ancestors protected with a nearly round the clock group of protectors - who evers sleep cycle woke them up when ever.
This is a just so story. If we all had the same sleep patterns, you could just as well point out that there would also be advantages to that arrangement.
> It isn't good enough to see what's going on when it's actually pitch black, which it is most of the time at night.
You mean in a thunderstorm, maybe? Or a fog bank?
On a clear night, even with no moon, humans can see quite well. Since rod vision is used, it is difficult to do fine work (reading, sewing, soldering, ....), but just walking around outside is no problem.
If you want to see the night for yourself, try spending a few nights camping out somewhere away from artificial lighting. Don’t bring along any of those terrible “white” LED flashlights – they completely clobber night vision. It takes about a half hour for eyes to fully adapt to the dark.
> It isn't good enough to see what's going on when it's actually pitch black, which it is most of the time at night.
It's pitch-black for city dwellers with eyes unadapted to darkness. Weather allowing, for most of the time you have moonlight providing good enough illumination to (carefully) navigate the outside.
Matthew Walker, PhD in his book "Why We Sleep" discussed sleep cycles and their variances from one person to the next. Specifically, during his discussion of circadian rhythm in chapter 2. From page 22: "As a social species, should we not all be synchronized and therefore awake at the same time to promote maximal human interactions? Perhaps not. As we'll discover later in this book, humans likely evolved to co-sleep as families or even whole tribes, not alone or as couples. Appreciating this evolutionary context, the benefits of such genetically programmed variation in sleep/wake timing preferences can be understood. The night owls in the group would not be going to sleep until one or two a.m., and not waking until nine or ten. [...] Consequently the group as a whole is only collectively vulnerable."
He discussed varying sleep cycles across individuals. Specifically, he suggested society needs to be more inclusive of different sleep patterns and needs. Instead, society rewards people who naturally wake early in the morning at the cost of "night owls". All in the same area of the book.
You're welcome to research and earn your own PhD in neurology and author your own book on sleep patterns, but I'll stick with Dr Walker's work.
I’m against the hypothesis though, if only for the fact that energy levels peak shortly after waking up - “why we sleep” discusses this a little.
That book also suggests the variety of sleep patterns exists for evolutionary reasons. Ie we are social creatures. Having a multitude of waking/restful cycles in a group kept our ancestors protected with a nearly round the clock group of protectors - who evers sleep cycle woke them up when ever.