Most of us have some degree of preference for late nights or early mornings. Where an individual falls on this spectrum largely determines his or her chronotype—an individual disposition toward the timing of daily periods of activity and rest. Some of us are clearly “larks”—early risers—while others of us are distinctly night owls. The rest of us fall somewhere in between the two.
We’re learning that these night owl and early riser tendencies are driven by some significant degree by biological and genetic forces. Different chronotypes are associated with genetic variations, as well as differences in lifestyle and mood disposition, cognitive function and risks for health problems, including sleep disorders and depression.
New research has now found evidence of physical differences in the brains of different chronotypes. ...
... But other research has also shown that the inclinations toward staying up late or rising early are deeply rooted in biological and genetic differences ...
Night Owls and Early Risers Have Different Brain Structures
Like to Stay Up Late? Different Neural Structures Found in the Brains of Night Owls
Why the Sleep-Deprived Crave Junk Food and Buy Higher Calorie Foods
The Mysteries of Intelligence ("Intelligence" as in Intellect, not "Intelligence" as in Spook Stuff)