[koenigdavidmj]

> Once I caught up on my sleep something funny started to happen. I would only sleep about 4 hours, then wake up for 2 hrs in the middle of the night

Some are convinced that this was our sleep pattern before electric lighting was a thing:

https://en.wikipedia.org/wiki/Segmented_sleep

[arawde]

There's also http://aeon.co/magazine/psychology/why-broken-sleep-is-a-gol... which was posted a while back on HN and which I found quite interesting.