I meant the expectation of how much to sleep. It's often claimed that in the past people slept much more, but hunter gatherers actually sleep on average 6.5 hours a night.

http://www.bbc.com/future/story/20170220-the-surprising-trut...

Siesta cultures a.o.

I meant quantity. That's moving some to a different time.

Siesta culture means sleeping an hour after lunch when the sun is higher and is more dangerous. You don't change your sleep hours because of that.