I believe that our primal ancestors slept many times during the day. The concept of a solid 8 hours was not really possible probably. They slept until they woke, then got up and did something. Going to bed at dark and getting up with the sun is a popular myth, but I do not think many animals, predators anyway, do this. Hunting is better at night. And since the tigers are hunting at night, humans had better be on guard too. Watch your dogs and cats. They are up and down all day and all night.
If you have a 9 to 5 job, napping might be difficult. But I always find plenty of opportunity to nap. I sleep until I wake up, then do something, day or night. I live in Thailand and this is normal here. Have to wait for an hour? Sleep. Waiting in the doctors office? Sleep. You see people sleeping on the side of the road here!!! Tired of walking? Sleep! lol
So I have started this pattern too. I sleep if I am sleepy, day or night. I NEVER lay in bed and toss and turn. I get up and do something. Then sleep another time. I notice that on a primal diet and lifestyle, my metabolism is much higher and I don't have the deep long sleeps that I used to have. A couple of hours of good sleep and I am ready to go!
Anyway, curious about other thoughts...