Modern life can negatively affect our sleep because of our exposure to electric light, less sunlight, poor exercise, and even dietary intake.
After the invention of the light bulb, becoming a night owl became more feasible.
Scientists at the University of Colorado Boulder performed a study into modern life and the sleep cycle.
They recruited eight volunteers and, after time has been spent outdoors, researchers claim that their body clocks re-synchronised with sunrise and sunset - just like our ancient forefathers.
Most life forms on Earth that are exposed to sunlight have evolved biological rhythms that anticipate its rise and set.