I was convinced we sleep less at night than pre-industrial man ..... that the electric light, phones, tvs, and busy schedules shaved hours off every day's rest. It appears to be untrue. Sleep time is a species characteristic more than a cultural one.
Jerome Siegel of the University of California (Los Angeles) decided to measure sleep time in three hunter gatherer tribes, two in Africa and one in the Bolivian jungle. The lean men pictured from the San tribe in Namibia don't look like world wide web people. Sleep averaged out six to seven hours! People didn't go to bed until several hours after sunset and generally got up a little ahead of dawn.