Why have industrialized societies adopted a sleep period asymmetrical to midnight?

Cheap, clean artificial lighting allows us to stay up long after dusk. On the other hand, it does not require us to. Is there a commonly accepted explanation why societies that have the means to shift the customary sleep period backwards, invariably do so?

The first question I’d ask is whether it’s just industrialised societies. You don’t need any more lighting than a small camp fire to stay up after sunset. Wouldn’t hunter/gatherer societies stay up late, eating the food gathered during the day and socialising? You then sleep until the sunrise wakes you up in the morning.

Temperature. The coldest temperature of the day is usually between 3 and 5 am, not at midnight. Not only does the body respond to temperature changes with sleep cues, but sleeping midnight to 8 am would do a better job of keeping you warm than sleeping 8 pm to 4 am.

Because getting up before dawn is difficult and mildly depressing. If you sleep at sunset, say, 7:30pm, youre getting up around 2 or 3am. There’s no sun.

I imagine our sleep schedules have more to do with how farming works then with how offices/factories work.

Around here, the bars are open until 2 a.m. Some until 4 a.m. That’s my reason…TRM

You can decide on the spur of the moment to stay up a little later.

But you can’t decide on the spur of the moment to wake up earlier. You’re asleep. You can’t decide anything.

So there’s a definite bias in favor of adding additional waking time at the end of the day instead of the beginning.

In my experience staying in small remote Indian villages without electricity, this is the case. People stay up with a lantern or around a fire chatting or telling stories for several hours after sunset.

Under primitive conditions, dawn serves to synchronize most people’s getting-up time. Assuming that most people need about 8 hours sleep, if they stay up for 16 hours they will have stayed up for several hours after dawn.

Modern industrialized society differs from primitive ones not in staying up after dark, but in often sleeping in after dawn.