... In the rest you seem to overlook that there is enough time for reproduction
and many kinds just having certain times for that so that that sleep does not
have to be in the way of the ability to have children, all the more for a
woman, as when the time comes there might be enough males there and maybe even
more than appreciated.
... Also in sleep not as much energy is used.
> It could be recuperative, such as replenishing neurotransmitter stores.<
Maybe, I don't know.