Before the invention of the light bulb, most people slept 3 hours longer than we do now.
Before Thomas Edison’s electric light came out in 1879, people used to sleep for 10 hours every night. In the ensuing 100 years, people have gradually reduced the amount of time they sleep by 20%. That number has continued to decline in recent years. Now people sleep close to 7 hours every night. We no longer need to base our sleep schedules on the sun.