What would happen if birth control were provided to women free of charge? A lot of good things. A recent study in the journal Obstetrics & Gynecology showed a dramatic decrease in abortion rates among women who were given free contraception. But the implications of the study are far bigger, and longer lasting, than just preventing abortion. Those implications have to do with what happens when unwanted pregnancies turn into babies. They show why conservatives ought to be supporting easily available contraception, not opposing it.

Some 9,250 women, ages 14 to 45, participated in the study, called CHOICE, conducted by researchers from Washington University in St. Louis. Over a three-year period, these women had abortions at a rate of 4.4 to 7.5 per 1,000. The national rate is about 19.5 per 1,000. The experiment also slashed the teen birth rate. The rate among teen girls in the U.S. is about 34.3 per 1,000. The birth rate among teens in CHOICE was 6.3 per 1,000.

Beyond cutting down on abortion, how could free birth control have a profound effect on society? Let’s say a single woman can’t afford birth control, or, like many teens, can’t get access to it, and gets pregnant. Even if she is well-intentioned and determined to do the best she can for her child, she may face tremendous economic and social pressure. She may not have a job. Even if she does, a mother can’t nurture if she’s working a double shift at the UPS warehouse. The effects of such stress can reverberate for many years, into another generation, and throughout society.

That’s because human beings have a “social brain.” It helps us to distinguish friend from foe, to cooperate with others, to protect our territory, to nurture our children, to drive us to have sex, to fall in love, to do business. Every individual’s social brain helps form the collective, society-wide social brain. So what happens in each of our brains matters to all of us. But sometimes the social brain doesn’t work as well as it should. In addition to diagnosable mental disorders that affect the social brain, like autism, research shows that simple neglect can also lead to social deficits.

As a recent article in The Harvard Review of Psychiatry pointed out, children who spent part of infancy institutionalized in orphanages “often show poor attention, hyperactivity, difficulty with emotion regulation, elevated levels of anxiety, increased rates of attachment disorders, and indiscriminate friendliness.” Such effects can be traced, at least in part, to the way neglect affects signaling neurochemicals, like the hormone oxytocin.

In researching our new book, The Chemistry Between Us: Love, Sex and the Science of Attraction, we met a young woman who’d been adopted from a Romanian orphanage by loving American parents in 1989, after the fall of the dictator Nicolae Ceausescu. She was 27 months old back then, and had spent almost all of that time living in absurdly neglectful conditions nearly devoid of human contact or nurturing. She grew up with nurturing parents. Yet today she is a ball of anxiety. She experiences overwhelming nervousness around anything medical, perhaps due to the hospital-style crib she was kept in for many hours a day. Power cords upset her. So does a break in routine. And she’s never really bonded emotionally with her adoptive mother—or anybody else. Other Romanian orphans adopted during that era show the effects of that deprivation even after decades of living in warm, caring households. Some are almost autistic in their social blindness and inability to bond.

Studies and experiments with both animals and humans show these adult problems are rooted, at least in part, in how very early life experience interacted with genes. As elucidated by Prof. Frances Champagne, now of Columbia University, and others, a mechanism called epigenetics—how genes can be physically changed in reaction to environment—can help set the course of later behavior, far into adulthood.

Champagne, for example, showed that rats born into a low-nurturing, neglectful environment had changes in genes related to stress hormones, and estrogen and oxytocin. (Both of those neurochemicals help promote social bonds.) This altered brain function. The rats grew up anxious, aggressive, stressed. They tended to have sex earlier, and female rats weren’t choosy about which males they had sex with. And when those daughters had babies of their own, they were less motivated to nurture; their experience as babies helped “program” their brains to receive less reward from nurturing, so they became low nurturers themselves. The cycle repeats from one generation to the next.

Being a stressed-out single mother can lead to this critical lack of nurturing. In one study, Prof. Todd Ahern, now at Quinnipiac University in Connecticut, removed fathers from monogamous prairie-vole family units, finding that single mothers—who had to bear the full load of keeping their families alive—could not compensate for the absence of the fathers. The pups got less attention. Daughters almost always grew up to become low-nurturing mothers themselves. Sons grew up to become less likely to form bonds with mates, making another generation of single-parent vole families more likely.

Of course, this doesn’t mean the same cycle is inevitable for a human single mother. But it does illustrate why early family life matters. Michael Meaney, a scientist at McGill University, and his colleagues, who have examined brain tissue of dozens of suicide victims, have shown that those who suffered abuse or neglect in childhood have the kinds of epigenetic changes found in Champagne’s low-nurturing rats and their offspring. Other findings in human populations over the last decade have corroborated the links between very early life stress, poor nurturing, and later adult behavior.

It’s not news that if we’re born into a deprived or low-nurturing home, we have a greater chance of growing up anxious and low-nurturing ourselves—and acting out the social consequences of that early experience. What is news is that we’re learning so much about why this happens—and to a large degree it’s due to changes in the chemistry of the social brain. We’re not saying that single-parent or poor families dealing with unintended pregnancies are doomed to produce socially dysfunctional children. A poor single mother, for instance, can benefit from social support for distressed families. Such interventions can help interrupt the cycle.

And so can free birth control.