Researchers studying religion in America have long observed a kind of faith-based law of gravity: While young people often stray, most return to the pews after they get married and have children.

But something new is happening, especially among the "nones" -- the growing ranks of individuals who declare themselves "unaffiliated," when it comes to religious life. While researchers have dissected their political views, now it's time to focus on their actions linked to marriage and children.

"We have always known that family size is related to religiosity. The more devout people are the more likely they are to get married and have a higher number of children," said John Green of the University of Akron, a veteran researcher on faith and public life.

But Americans born after the 1960s have been shaped by storms of change linked to sexuality and marriage. For them, noted Green, contraception and abortion are normal parts of the American way of life. Cohabitation rates keep rising and people tend to marry later than in the past. Thus, they are older if and when they choose to have children.

It's time to probe the impact of these trends on religion, said Green, in a telephone interview. He was reacting to the Pew Research Center's massive 2014 U.S. Religious Landscape Study, released on Nov. 3.

"You used to be able to say that the young would drift away from the faith of their youth, but then they would get married and have kids and that would pull them back … or maybe they would choose some other faith," he said. "The assumption was that marriage and family change people and they get more religious as they get older.

"Maybe what we're seeing now is that it's the faith component that is actually driving the actions of the young people who are choosing to get married and to have children in the first place. … Turn that around and maybe more and more Americans are never going to get married and they're never going to have kids and settle down."

In other words, noted Green, if people who have strong religious beliefs are more likely to get married and have children, then it may be just as natural for many of those who reject religious traditions on sex and marriage to join the growing niche of atheists, agnostics and the "religiously unaffiliated." Thus, many of these "nones" may never experience the family-centered impulse to return to faith as they age.

The Pew Research Center team noted that, "in the seven years since the first Religious Landscape Study was conducted, no generational cohort has become more religious as measured by self-assessments of religion's importance in their lives, frequency of prayer or frequency of church attendance. Indeed, older Millennials -- adults who were between the ages of 18 and 26 when the first Religious Landscape Study was conducted in 2007 and who today are in their late 20s and early 30s -- are, if anything, LESS religiously observant today than they were in 2007 in these important ways. The share of older Millennials who say they seldom or never attend religious services has risen by 9 percentage points."

While a rising number of Americans are becoming less religious, the 2014 study noted that there is no evidence of declining commitment among Americans who actively practice their faith. This belief vs. unbelief chasm is growing.

The study noted, "religiously affiliated people appear to have grown more religiously observant. …The portion of religiously affiliated adults who say they regularly read scripture, share their faith with others and participate in small prayer groups or scripture study groups all have increased modestly since 2007." In fact, the rising share of adults who engage in these practices has helped many traditional religious groups hold their own, "despite the rapid growth of the religious 'nones.' "

Still, Green said it's obvious that religious leaders must "consider whether there is something essentially different about this Millennial generation when it comes to matters of faith." In fact, sweeping changes in behaviors linked to sex and marriage may signal the "creation of a something new and important -- a large, separate, truly secular subculture in the American population. …

"That will affect all of American life, including the lives of traditional religious believers."