All humans are created unequal. You are bigger and stronger than Pop; I am bigger and stronger than Hilda. I have the least years of experience; Pop has the most. Pop is a super-genius...but he concentrates so hard that he forgets to eat...unless he has a nursemaid to watch him—as Mama did, as I did, as Hilda now does. You, sir, are the all-around most competent man I’ve ever met, whether driving a duo, or dancing, or telling outrageous tales. Three of us have eight or nine earned degrees...but Aunt Hilda with none is a walking encyclopedia from insatiable curiosity and extraordinary memory. We two are baby factories and you two are not—but two men can impregnate fifty women—or five hundred. There is no end to the ways that we four are unequal.
Robert A. Heinlein