"The human egg is 85,000 times larger than the human sperm. The consequences of this gematic dimporphism ramify throughout the biology and physiology of human sex. The most important result is that the female places a greater investment in each of her sex cells. A woman can expect to produce only about 400 eggs in her lifetime. Of these a maximum of about 20 can be converted into healthy infants. The costs of bringing an infant to term and caring for it afterward are relatively enormous. In contrast a man releases 100 million sperm with each ejaculation. Once he has achieved fertilization his purely physical commitment has ended. His genes will benefit equally with those of the female, but his investment will be far less than hers unless she can induce him to contribute to the care of the offspring. If a man were given total freedom to act, he could theoretically inseminate thousands of women in his lifetime."

- On human nature by Edward Osborne Wilson