I understand in the time before industrialization humans did a 2 sleep cycle. Go to bed at dusk and sleep for 4 hours or so and then get up and do some reading, hanky panky, and family talk time. Doctors of the time said sex between sleeps was the best for conceiving. When street lights were invented and industrialization came along, the church, government, and business got together and created the 8 hours of work, 8 hours to yourself, and 8 hours of sleep. Humans were never meant to sleep the way we are forced to today.