https://www.sciencealert.com/humans-used-to-sleep-in-two-shi...
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> 25 adults...with late sleep schedules and subclinical features of delayed sleep phase disorder (DSPD).
The "subclinical features" part is important! I am not trying to step into the "habits versus nature" part for healthy night owls / morning larks, but actual clinical DPSD is a significant medical problem that is very clearly not related to habits or sleep hygiene. Which means comments like this:
> Before the industrial revolution few were staying up all night regularly unless they were on night shift. Bright light and multimedia available at night changed.
are truly irrelevant here, and inappropriately judgmental of people with a real illness.
There are still valuable things that can be learned from that kind of research, but the popular coverage really missed the mark by directly extrapolating from research in mice to human circadian rhythms.
People are downplaying the extent to which habits and preferences have an impact. Staying in bed late will shift forward your circadian rhythm. Blue-light emitting electronics will suppress melatonin at night and raise cortisol.
Before the industrial revolution few were staying up all night regularly unless they were on night shift. Bright light and multimedia available at night changed.