I read awhile back that alot of people naturally sleep for 4-6 hours, wake up for awhile and then sleep another 2+ hours. Many people can't sleep 8 hours straight on a regular basis and there's probably some evolutionary benefit to it all.

But many of us don't give ourselves enough time to do it... we just subsist on the intial 4-6 bc we have to stay up late or be up early and can't dedicate enough total time to get enough sleep.

I'm working on this myself bc I've had too many nights where I'm in bed by 11 and up at 430 and struggling through the rest of the day. I'd probably have to be in bed by 9pm to get 8 hours in by 6am the next morning.