Some of it is genetic but mostly it's conditioning, like in the Military.
EDIT: To clarify, veterans often (but not always) wake up before dawn consistently for decades after their service. I don't really recommend it as an option, but it's proof of concept.
Yeah, I got the conditioning during college. Work 32 hours a week while taking 15 credits, you won't have time for sleep. Work 7:30am-4pm MWF, go right to campus for some homework and dinner before class 6pm-9pm. Then go home and do homework/sleep. Tu/Tr have class from 10am-2pm and work 3pm-7pm and then work on homework, housework, gym. You won't have the energy to stay up late.
Some of it is genetic but mostly it's conditioning, like in the Military.
EDIT: To clarify, veterans often (but not always) wake up before dawn consistently for decades after their service. I don't really recommend it as an option, but it's proof of concept.
Kids, kid's sports and work. Or conditioning, like you said
Yeah, I got the conditioning during college. Work 32 hours a week while taking 15 credits, you won't have time for sleep. Work 7:30am-4pm MWF, go right to campus for some homework and dinner before class 6pm-9pm. Then go home and do homework/sleep. Tu/Tr have class from 10am-2pm and work 3pm-7pm and then work on homework, housework, gym. You won't have the energy to stay up late.