Im guessing that we humans will be more efficient someday. LoL, how ironic, my char's name is Darwin rofl.
Anyway, probably someday a person will be born that can function fully with only a couple hours of sleep. During this time, this person could have lots and lots of sex with multiple partners, thus passing his genes along to his children. These children will have children, and their childrens children will have children, and pretty soon this more efficient human being will become the american standard.