Or they used to have a drawback that is no longer relevant. I'm thinking for instance that the world's longest continuous culture considers 'dreamtime' to be mo

Or they used to have a drawback that is no longer relevant. I'm thinking for instance that the world's longest continuous culture considers 'dreamtime' to be more important in some ways than the waking world. It may be that the functions which used to require 8 hours of sleep can be done during waking hours as well, perhaps through greater caloric intake or more articulated mythologizing.