Theories of human sleep still seem very speculative. I sometimes wonder if there's some function of sleep that's essential to higher intelligence. And if AGIs would need a similar function? 
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ISTR an argument that a forced period of inactivity during the darkness helped avoid predators with better night vision. Doesn’t seem crazier to me than, eg, fight-or-flight.
A problem with the predator theory is that some apex predators sleep a lot. Lions and tigers sleep 18-20 hours a day.
