man-woman polarity.

from Stranger in a Strange Land by Robert Heinlein

pg 104

"The man-woman polarity which controlled all human lives could not exist on Mars.....human bipolarity was both the binding force and the driving energy for all human behavior, from sonnets to nuclear equations. If any being thinks that human psychologists exaggerate on this point, let it search the Terran patent offices, libraries, and art galleries for creations of eunuchs."