Richard Wrangham estimates hominins tamed fire and started cooking with it 1.8 million years ago
I heard about segmented sleep a couple years ago. The idea is that you sleep for maybe three hours, then get up and putter around for two or three hours, then go back to sleep for another three or four hours.
The easy availability of light after sunset has changed our sleeping patterns only recently, on an evolutionary scale. Before we had electric lights, candles, oil and gas lamps, our only sources of artificial light after sundown were campfires and short-lived torches.
Karen Emslie has an article on segmented sleep at Aeon. A snippet:
Before electric lighting, night was associated with crime and fear – people stayed inside and went early to bed. The time of their first sleep varied with season and social class, but usually commenced a couple of hours after dusk and lasted for three or four hours until, in the middle of the night, people naturally woke up. Prior to electric lighting, wealthier households often had other forms of artificial light – for instance, gas lamps – and in turn went to bed later. Interestingly, Ekirch found less reference to segmented sleep in personal papers from such households.
For those who indulged, however, night-waking was used for activities such as reading, praying and writing, untangling dreams, talking to sleeping partners or making love. As Ekirch points out, after a hard day of labouring, people were often too tired for amorous activities at ‘first’ bedtime (which might strike a chord with many busy people today) but, when they woke in the night, our ancestors were refreshed and ready for action. After various nocturnal activities, people became drowsy again and slipped into their second sleep cycle (also for three or four hours) before rising to a new day. We too can imagine, for example, going to bed at 9pm on a winter night, waking at midnight, reading and chatting until around 2am, then sleeping again until 6am.
Think about this if you have insomnia that wakes you in the middle of the night and you can’t get back to sleep. It may not be a detrimental condition that requires medication or other intervention. Can you really win a fight with a million years of evolution?
Steve Parker, M.D.