Apparently, sleeping eight hours straight in a row is a fairly
recent development. As recently as a century ago, people slept
in two four-hour chunks: In the early 1990s, psychiatrist Thomas
Wehr conducted an experiment in which a group of people were
plunged into darkness for 14 hours every day for a month. It
took some time for their sleep to regulate but by the fourth
week the subjects settled into a very distinct sleeping pattern.
They slept first for four hours, then woke for one or two hours
before falling into a second four-hour sleep. Sounds like
something that happens only in the lab, right? Well apparently,
there are hundreds of references to this “segmented sleeping
patterns” in the historical record. According to the BBC, “these
references describe a first sleep which began about two hours
after dusk, followed by waking period of one or two hours and
then a second sleep.” What did people do during this “waking
period”? [T]hese hours weren’t entirely solitary – people often
chatted to bed-fellows o