[gwd]

Jared Diamond in "The World Until Yesterday" says that when he was on expeditions with natives in New Guinea, they would all go to sleep when the sun went down (near the equator so usually pretty close to 7pm), then wake up around midnight and chat for an hour or two around the fire, before going back to sleep again and waking up at sunrise (again around 5 or 6).

[elric]

That's 10 hours of sleep at night? Or are you being euphemistically and are you including time spent on sex?

[viklove]

7-12 (5 hours sleep) 12-2 (2 hours chatting around fire) 2-5 (3 hours sleep)

How are you doing the math here? I count 8 hours of sleep.