“In the first place there is no instinctive purpose for the sex drive; people, not nature, give it a purpose. Sex can be used to express love, show affection, provide physical pleasure, or it can be used for procreation. Nature endowed women with the capability of having children but there is no innate drive which says they must use that capability. More than anything else it was the inability of women to prevent pregnancy which made them think that procreation was the reason for their sexual desires. In the past, birth control methods were either inadequate or totally lacking so when women made love they made babies. There was a pretty good correlation between copulation and procreation and that gave rise to some faulty cause-and-effect thinking: Sexuality creates a physical drive that must be satisfied. The satisfaction of that drive often causes pregnancy. Ergo, the reason for the drive was to become a mother.
This false logic put procreation in the same category as eating, drinking, sleeping, defecating, and breathing. The distinction that people failed to draw was that the latter drives have to be satisfied in order for people to go on living. They are true instincts. A woman, on the other hand, who fails to have children does not die. Consider the food intake instinct. People can diet, fast…but they cannot go on indefinitely without food…The basic nature of an instinct is that it cannot be ignored for long without causing harm. But women can use some method of birth control each time they have intercourse and never suffer as a result. If procreation were an instinct, women would die from extended use of contraception. Since they do not, it is obvious that having babies is not a biological drive.” – Anna and Arnold Silverman, The Case Against Having Children.