I think there's an evolutionary advantage to this. If you don't commit new memories when sleep-deprived, then you don't remember how rough the first few months

I think there's an evolutionary advantage to this. If you don't commit new memories when sleep-deprived, then you don't remember how rough the first few months of parenting a newborn can be (you get very little sleep during that time) and you're more likely to have more children.