Throughout history, men learned that survival, respect and women's love were all achieved by making a killing –whether killing animals, killing enemies, or making a killing on Wall Street. Women received the money that men produced by loving. Men came to feel themselves as unlovable without the money, property or the heroism it took to make them equal to a woman's love. Women came to associate men spending money on them as a statement of how much they were valued—even loved— by the man. Her ability to love became her source of security: a diamond is a girl's best friend. Essentially this dynamic is true in almost all societies and all classes throughout history.

p. 135. - Why Men Earn More (2005)