We still think of the archetypal unwed mother as a Jamie Lynn Spears—a dopey teenager who dropped her panties and got in over her head. A generation and more ago, that’s who most unwed mothers were. But according to the most recent statistics from the Centers for Disease Control, teenagers account for only 23 percent of current out-of-wedlock births. That means the vast majority of unwed mothers are old enough to know what they’re doing: Unwed births are surging among women ages 25 to 29.

In the last 50 years, there has been an extraordinary decoupling of marriage and procreation. In 1960 about 5 percent of births were to unwed mothers; that figure is now a record high of nearly 40 percent. Out-of-wedlock births used to be such a source of shame that families tried to hide them: Singer Bobby Darin was born to a teen mother and raised to believe she was his sister. But now out-of-wedlock births are greeted with a shrug. Some say they’re an understandable response to economic realities. Others say they’re a liberating change from the shotgun-wedding ethic that shackled two unsuitable people together for life.

As Slate’s advice columnist, Dear Prudence, I get constant reports from the people who are creating the statistics. When I extol the importance of marriage in the advice column, my inbox fills with e-mails from readers who don’t see marriage as the passage from single life to a life of commitment. To them, the marriage certificate is the first document in a paper trail that will end with a divorce decree. This doesn’t mean my correspondents conclude that men and women shouldn’t form unions and even live together, just that it may be wiser not to make your love life official. "Legal ties are supposed to make it somehow legit? With the divorce rate as high as it is, a live-in girlfriend is just as good," wrote one.

Readers also like to rebuke me for my preference that two decent people who are committed to each other and find themselves procreating without intending to should provide the stability of marriage for their child. "Having a child will be stressful and life altering enough. Parents need to work on their relationship on their time schedule." "I feel that a baby is its own blessing. Have that blessing before you get married." "How dare you imply that an unexpected pregnancy should lead to marriage? You are simply out of touch with modern culture."

That may be. But it also means that modern culture is out of touch with the needs of children. Some researchers identify out-of-wedlock births as the chief cause for the increasing stratification and inequality of American life, the first step that casts children into an ever more rigid caste system. Studies have found that children born to single mothers are vastly more likely to be poor, have behavioral and psychological problems, drop out of high school, and themselves go on to have out-of-wedlock children.

For 10 years, the Fragile Families and Child Wellbeing Study at Princeton University has followed the families of 5,000 children, three-quarters born to unwed parents. According to the research, most of these parents, both women and men, said they wanted to get married—and to each other. But they somehow feel this mutual decision is beyond their power to make. And by not making it, the forces of inertia start pulling them apart. Five years after their children’s births, only 16 percent of the couples had married, and 60 percent had split.

Among the most poignant letters I get are those from young women wondering whether they will ever convince the father of their children finally to marry them. "My boyfriend and I have a 4-year-old son. We’ve broken up but realized that we truly are meant for one another. My father was diagnosed with stage four cancer last year, and I’ve made it known to my boyfriend how important it is for me to have my father with me when I get married. When I bring up marriage to my boyfriend his reply is we will get married, I promise, but he has not asked me."

That out-of-wedlock births are a problem for society does get some political attention—the kind of attention that shows there’s not a good plan for what to do about them. Mitt Romney mentioned the statistics in his presidential withdrawal speech. He cites declining religious observance, easily available pornography, and the possibility of gay marriage as the causes—a platform that seems unlikely to reverse the birth trends. Barack Obama, who grew up without a father, believes that a central reason for the ever-increasing rates is the difficult economic circumstances of the working class. In one speech on fatherhood, he talked about the need for government programs to help men become more of a presence in their children’s lives and admonished fathers to take their duties seriously. But he didn’t mention that one key to effective fatherhood is first becoming a husband.

Economists believe humans act rationally (a somewhat irrational belief, if you ask me), so some conclude that all this out-of-wedlock childbearing is a logical response to market forces, not the result of something as amorphous as "culture." Since many working-class men do not offer the financial stability they used to provide, women see little incentive to marry them. As Obama said, "[M]any black men simply cannot afford to raise a family." (The out-of-wedlock birthrate among black Americans is close to 70 percent.) I’m trying to follow the logic here. I can understand that a woman looking to get married may decide that a man is such a poor economic prospect that he’s not husband material (even if a husband with a low income is better than no husband and no income). But how then is that same man, or a string of them, worthy of fathering her children?

Scholar Kay Hymowitz, author of Marriage and Caste in America: Separate and Unequal Families in a Post-Marital Age, turns the argument around and says it’s not that harsh economic conditions lead to women having children without fathers, but that the decision to have children without fathers leads to harsh, and self-perpetuating, economic conditions. She explains that having the belief that a solid marriage is central to one’s life—that it precedes starting a family—encourages woman and men to make important choices based on self-discipline and deliberation. This is a formula "needed for upward mobility, qualities all the more important in a tough new knowledge economy."

I get letters all the time that describe the turbulence that results from deciding marriage is archaic. Sometimes the writers start with a conflicted sense of hope. "My ex is rather immature and irresponsible. I had a recent fling with him that resulted in pregnancy. I am overjoyed with the impending arrival of my baby, but I fear that no one else in my life will feel the same way." This is followed by more conflicted and less hopeful letters when the kids are small. "My boyfriend and I have a child who is almost 2. He also has a daughter and I have two other children. We bought a home together, but a week before we were about to move in, he left me. Now it’s four months later, and he’s bought me an engagement ring, but I found out he had a girlfriend during the time we were split." "I have two children with my ex-boyfriend. We broke up because last year a paternity test he was ordered to have came back positive. Even though we are not together, I still want my kids to have a father in their life. I also know he is ignoring his new son because he wants nothing to do with the mom, but that little boy also deserves to have a male figure who cares."

Having unmarried parents can be devastating for children who start out with no cushion in life. In 1999 congressional testimony, Isabel Sawhill of the Brookings Institution said that the increase in single-parent families—mostly due to unwed motherhood in the past few decades—"can account for virtually all of the increase in child poverty since 1970." A recent study found that the stress of early childhood poverty can literally damage developing brains.

Hymowitz points out that all classes of Americans once followed the same life script of marriage before children. When divorce rates started soaring in the 1970s, everyone was fleeing their marriages. But then the classes started diverging. The Economist cites statistics that show among college-educated women married between 1990 and 1994, only 16.5 percent were divorced 10 years later. Among those with a high-school education or less who married in those same years, about 40 percent were divorced after a decade.

And to avoid the trauma of divorce, those with less education began forgoing marriage altogether. Better-educated women, who once upon a time were at a disadvantage in finding a mate, "are now more likely to marry than their non-college peers," according to the National Marriage Project at Rutgers University. It turns out that outside Hollywood, there aren’t too many Murphy Browns—successful, educated women who choose to have children alone. The Murphy Browns actually get married: Only 4 percent of college graduates have children out of wedlock.

It’s important to offer some caveats. I am not—the researchers are not—advising marriage at all costs. "Dear Prudence" letter writers should not marry the jerks whom they had drunken procreative sex with and hope never to see again. Nor do I recommend entering into a union with a clearly unstable, unsuitable partner. A survey by the Center for Law and Social Policy on the benefits for children of having married parents did come to the anodyne conclusion that "high conflict" marriages can be as bad for children as having never-married parents. I know. My parents had a "high conflict," violent marriage; I don’t recommend it for anyone. Also, growing up in ideal circumstances is no guarantee that one’s life will be a happy success, just as growing up in difficult ones does not doom one to be a troubled failure. (See Barack Obama.)

But perhaps in our desire not to make moral judgments about personal choices, young women wholly unprepared to be mothers are not getting the message that there are dire consequences of having (unprotected) sex with guys too lame to be fathers. There is a scene in the teen pregnancy movie Juno in which the title character, a 16-year-old who has decided not to abort her unplanned baby but to give it up for adoption, is having an ultrasound. The technician, thinking she has on the examining table another knocked-up teenager planning to raise her child, makes disparaging remarks about children born into those circumstances. We are supposed to loathe this character and cheer when Juno’s stepmother puts her in her place. But I found myself sympathetic to the technician. Why is it verboten to express the truth that growing up with a lonely, overwhelmed mother and a missing father is a recipe for childhood pain?

Why do Hispanic families seem more accepting of teenage out of wedlock pregnancies ?