Joshua M. Zeitz, lecturer in history at Cambridge University, writing in the NYT (Dec. 27, 2003):

Opponents of the emergency contraceptive, known as Plan B, say they are concerned that among other things, widening access to the morning-after pill will encourage sexual promiscuity, particularly among young people. It was this apprehension that led Dr. W. David Hager of the University of Kentucky to join three other committee members in voting against the recommendation. Dr. Hager said he worried that Plan B was no less revolutionary than the birth control pill, which he claims ushered in"a new day and age for the expression of sexuality among young people."

Dr. Hager's argument is a common one. Legalized by the F.D.A. in 1960,"the pill" has been widely described as starting a revolution in sexuality and morals. But that is based on a misunderstanding of the history of America's sexual revolution and the pill's role in it.

Before 1960, the story goes, the natural constraints of human biology held Americans to strict standards of sexual discipline; after 1960, and after the pill, Americans threw off the shackles (or, depending on one's political perspective, the civilizing influence) of sexual propriety. Ever since, we've been either slouching toward Gomorrah or, as Clare Boothe Luce once famously announced, living in an age when the"modern woman is at last free as a man is free, to dispose of her own body, to earn her living, to pursue the improvement of her mind, to try a successful career."

That's a lot of power for one little pill. In truth, this narrative is flawed. Though the pill surely made contraception easier, and while it gave women more power and responsibility in family planning, it hardly created a sexual revolution. American sexual habits had been changing long before the pill found its way onto the market. Early sex surveys revealed that about half of all women who came of age in the 1920's admitted to engaging in premarital sex (defined as coitus), a figure that held steady for women in later decades.

Americans were also practicing birth control long before the pill. As early as 1938 a poll commissioned by The Ladies' Home Journal found that roughly four of every five women approved of using birth control. Just over two decades later, on the eve of the pill's legalization, 80 percent of white women and 60 percent of nonwhite women reported practicing some form of family planning.

Even the heightened sexual permissiveness of the 1960's can't be attributed to the pill. Throughout the better part of the decade doctors generally prescribed the first oral contraceptive, Enovid, only for married women, who made up the drug's largest market share in its early years. As late as 1971 only 15 percent of unmarried women age 15 to 19 used the pill. Even in recent times, only about 23 percent of women age 15 to 24 report using it.

The pill, then, did not create America's sexual revolution as much as it accelerated it. And that revolution had been a long time in the making.

Over the course of the 19th century the average number of children born to married couples dropped to about four from about seven. Americans probably weren't having less sex. Instead, couples — particularly those in the growing middle class, whose families no longer required legions of children to work on the farm — were practicing birth control. They were coming to view sex as an activity that wasn't merely procreative, but also central to pleasurable and loving marriages.

In the early 20th century many Americans began experimenting with sex outside of matrimony — partly because they could. By the 1920's a majority of Americans lived in urban areas where they enjoyed greater anonymity and social freedom. Meanwhile, a growing leisure culture provided a host of places — from dance halls to movie theaters — where men and women could meet.