The ruthless war of promiscuity

"A society in which conjugal infidelity is tolerated must always be in the long run a society adverse to women. Women, whatever a few male songs and satires may say to the contrary, are more naturally monogamous than men; it is a biological necessity. Where promiscuity prevails, they will therefore always be more often the victims than the culprits. Also, domestic happiness is more necessary to them than to us. And the quality by which they most easily hold a man, their beauty, decreases every year after they have come to maturity, but this does not happen to those qualities of personality -- women don't really care twopence about our looks -- by which we hold women. Thus in the ruthless war of promiscuity women are at a double disadvantage. They play for higher stakes and are also more likely to lose. I have no sympathy with moralists who frown at the increasing crudity of female provocativeness. These signs of desperate competition fill me with pity" (We Have No 'Right to Happiness', Lewis, 1963).

This was the last essay that C. S. Lewis wrote for publication, and it is definitely one of the most interesting Lewis essays.

I've been doing an informal study about this quote in particular. I've been asking people what they think is the "biological necessity" of monogamy for woman. I've gotten a lot of interesting opinions, and I really enjoying hearing what people have to say. There is also the question of what did Lewis mean by the "biological necessity" and what do we know now in science about the biological "necessities" of monogamy. Overall, I am very intrigued by the idea. I would love to hear your thoughts.

What is woman's "biological necessity" for monogamy?