The disruptive results for individuals and society spawned by the revolution in attitudes and behavior regarding sex, marriage, family, and childbearing that erupted a half-century ago have become too obvious to ignore. These things were predictable--in fact, some people actually predicted them from the start--but by now their impact has grown so painfully apparent that even secular voices are being raised in alarm.

The problems are increasingly visible in the United States. They include an aging population with fewer young workers to support the elderly, along with a disturbingly high incidence of disabilities among children born to parents who put off having them until their 30s and 40s and then, in many instances, resorted to drugs or reproductive technologies to achieve pregnancy.

Between 2007 and 2010, the U.S. birthrate dropped 8 percent, to the lowest level since 1920, when reliable data first became available. The lifetime average of 1.9 children per woman is below the replacement rate of 2.1--the number of children needed to keep population level. Granted, some of this is due to the recession but some reflects longer-term trends.

Religious sources, some of them anyway, began warning about such things a long time ago. In his 1968 encyclical condemning contraception, "Humanae Vitae," Pope Paul VI spoke of "insurmountable limits" to what people can rightly do to and with their bodies, and of the personal and social imperatives requiring that those limits be respected. The pope was ignored when he wasn't laughed at. But he was right.

Now, in their own way, secular sources have begun to make points very much like those made by Paul VI and a few others. As fresh evidence, consider recent articles in two very different opinion journals--the neoconservative Weekly Standard and the liberal New Republic. Both are required reading for people who want to know the dismal demographic future that, barring a miracle, lies just ahead.

Jonathan V. Last focuses in the Standard on the crisis in marriage. To put it simply, large numbers of Americans just aren't getting married any more.

Up until 1970, Last writes, the percentage who were married at some point in their lives never fell much below 93 percent. But now 67 percent of men and 57 percent of women in the prime childbearing years between 20 and 34 have never been married, and more than half of voting age Americans are single.

Over in the New Republic, Judith Shulevitz, the magazine's science editor and an older mother herself, notes that the age of first-time mothers rose from 21.5 in 1970 to 25.4 in 2010.

As the age of mothers has risen, birth defects also have increased among the children of older women who postponed pregnancy and then turned to technology to catch up. (Lest you wonder: the incidence of birth defects also is higher among children of older men.) Shulevitz suggests doctors get busy spreading the word "that tinkering with reproductive material at the very earliest stages of a fetus's growth may have molecular effects we're only beginning to understand."

Jonathan Last sees two large explanations for what has happened in recent decades: "the waning of religion in American life" and the shattering of the "iron triangle" that previously linked sex, marriage and childbearing. No doubt that is so. As Pope Paul VI said back in 1968, "The honest practice of regulation of birth demands...that husband and wife acquire and possess solid convictions concerning the true values of life and of the family." That was necessary then, and it's just as necessary today.

Russell Shaw is the author of more than twenty books, including three novels and volumes on ethics and moral theology. He is a consultor of the Pontifical Council for Social Communications.