Variability is one of the virtues of a woman. It avoids the crude requirement of polygamy. So long as you have one good wife you are sure to have a spiritual harem". - G.K. Chesterton
The facts of variability, of the struggle for existence, of adaptation to conditions, were notorious enough; but none of us had suspected that the road to the heart of the species problem lay through them, until Darwin and Wallace dispelled the darkness. - Thomas Henry Huxley