[spazbob]

This feels like one of those points that go back to our recent history vs the last 100,000 years of evolution.

Before artifical light, alarm clocks, jobs, screens with blue light etc - we presumably woke and slept fairly consistently, no doubt tied partly to sunlight and temperature. Some people probably slept more than others, as they always have, but I wouldn't be surprised if there was a lot more consistency.

Disclaimer: I know nothing, just interested