Sleep and nighttime awakening

Here is an article from the BBC on the naturally bimodal sleep patterns that predominated before artificial lighting kept people up late. A pretty good review, although it doesn’t mention that this was most common in the winter, when people were in bed for 14 hours a day, far longer than anyone could sleep. I’m not sure people had bimodal sleep when it was light until 11pm and the sun rose again at 6 am, which is still typical during the summer in northern Europe.