Depends when you're talking in history. It used to be normal not to have a day/night cycle, but a split of three. So that you would wake up to stoke the fire. S

Depends when you're talking in history. It used to be normal not to have a day/night cycle, but a split of three. So that you would wake up to stoke the fire. So, no, people did stay up very late before the invention of electricity. Humans adapt extremely well to their circumstances. You can obviously push it too far, but adaptation itself is natural.