That doesn't mean that having a 'late night' trait wasn't advantageous to mating. For example, when humans started pair bonding, infidelity may have been more common among those who could sneak out under the cover a darkness while their partner was asleep, spreading that trait further than those who remained monogamous. It is easy to think of many possible reasons why a late night trait could have been advantageous in spreading that trait further than those who naturally followed a more daytime rhythm during teenage years.
Or it could just be random chance. Either way, it's fun to discuss. We don't have to dismiss all fun discussion because it may be conjecture. It is only the comments section of HN, not a respected scientific publication. Time and place.
It is fun speculation, but still, OP's self-assured "this is so trivial" tone was not called for.
I'm positive they figured out how to have sex in the day as well when possible. But nomadic daytime marching would reduce opportunity, and in a hunting culture it would be harder to separate a woman because of daily gender-disparate activities. In a predominantly gatherer culture, perhaps it was easier.
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.
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'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.
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 grew up in upstate New York and could actually run 5 miles around the nearby lake in the woods any night, even moonless ones. You can see the silhouette of the trees against the stars and it isn't even really needed once you memorize the trail anyway. And that was just for exercise. I imagine horny teenagers would be even more hard working.