This is a neat article from BBC News today that goes over the evidence that people throughout history used to take two 4-hour sleeps per night, instead of a straight 8-hour stretch like today. The theory is that in a time with little civil protection (i.e. police), there was no benefit to being out and about after hours:
“Even the wealthy, who could afford candlelight, had better things to spend their money on. There was no prestige or social value associated with staying up all night.”
The theory is that humans slept for 4 hours soon after dusk and awoke for an hour or two around midnight before falling asleep for another 4 hours.
“During this waking period people were quite active. They often got up, went to the toilet or smoked tobacco and some even visited neighbours. Most people stayed in bed, read, wrote and often prayed.”
The Industrial Revolution’s change to more rigid and efficient schedules, combined with modern electricity changed this to our modern 8-hour stretch. It’s neat seeing how the way we structure our day is very much a modern construct. Even our Monday to Friday, 9 to 5 is new. In ancient Rome, for example, time was divided in two very different ways. First, there were festival days (and thus, days off) and non-festival days (work days). Second, there was the agricultural season (work days) and the non-agricultural season (days off).
The full article, with some of the supporting evidence, is here: [BBC News]