Quattro Musser, 17, of Portland, Ore. He and his friends don’t have any interest in drinking alcohol, and he thinks serious dating in high school doesn’t make sense. (Marlee Brown)

When 17-year-old Quattro Musser hangs out with friends, they don't drink beer or cruise around in cars with their dates. Rather, they stick to G-rated activities such as rock-climbing or talking about books.

They are in good company, according to a new study showing that teenagers are increasingly delaying activities that had long been seen as rites of passage into adulthood. The study, published Tuesday in the journal Child Development, found that the percentage of adolescents in the United States who have a driver's license, who have tried alcohol, who date and who work for pay has plummeted since 1976, with the most precipitous decreases in the past decade.

The declines appeared across racial, geographic and socioeconomic lines and in rural, urban and suburban areas.

To be sure, more than half of teens still engage in these activities, but the majorities have slimmed considerably. Between 1976 and 1979, 86 percent of high school seniors had gone on a date; between 2010 and 2015, only 63 percent had, the study found. During the same period, the portion that had ever earned money from working plunged from 76 percent to 55 percent. And the portion that had tried alcohol plummeted from 93 percent between 1976 and 1979 to 67 percent between 2010 and 2016.

Teens have also reported a steady decline in sexual activity in recent decades. The portion of high school students who'd had sex fell from 54 percent in 1991 to 41 percent in 2015, according to statistics from the Centers for Disease Control and Prevention.

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"People say, 'Oh, it's because teenagers are more responsible, or more lazy, or more boring,' but they're missing the larger trend," said Jean Twenge, lead author of the study, which drew on seven large time-lag surveys of Americans. Rather, she said, youths may be less interested in activities such as dating, driving or getting jobs because in today's society, they no longer need to be.

According to an evolutionary-psychology theory that a person's "life strategy" slows down or speeds up depending on the person's surroundings, exposure to a "harsh and unpredictable" environment leads to faster development, while a more resource-rich and secure environment has the opposite effect, the study said.

In the first scenario, "you'd have a lot of kids and be in survival mode, start having kids young, expect your kids will have kids young, and expect that there will be more diseases and fewer resources," said Twenge, a psychology professor at San Diego State University who is the author of "iGen: Why Today's Super-Connected Kids are Growing Up Less Rebellious, More Tolerant, Less Happy — and Completely Unprepared for Adulthood."

A century ago, when life expectancy was lower and college education less prevalent, "the goal back then was survival, not violin lessons by 5," Twenge said.

In that model, a teenage boy might be thinking more seriously about marriage, and driving a car and working for pay would be important for "establishing mate value based on procurement of resources," the study said.

But the United States is shifting more toward the slower model, and the change is apparent across the socioeconomic spectrum, Twenge said. "Even in families whose parents didn't have a college education . . . families are smaller, and the idea that children need to be carefully nurtured has really sunk in."

The postponement of "adult activities" could not be attributed to more homework or extracurricular activities, the study said, noting that teens today spend fewer hours on homework than they did in the 1990s and the same amount of time on extracurriculars (with the exception of community service, which has risen slightly.) Nor could the use of smartphones and the Internet be entirely the cause, the report said, since the decline began before they were widely available.

Musser, who lives in Portland, Ore., has had summer jobs, but he has never drunk alcohol and said he is not curious to try. To him, the idea that earlier generations of teens centered evening activities around procuring and drinking alcohol sounded mystifying.

"I haven't heard of anyone who goes out and specifically drinks with their friends," he said. "It's not something you set out to do, like, 'Oh yeah, I'm going to go out and get drunk.' "

In a city where it is easy to bike, take buses or ride-share, he doesn't see much need to drive. And as for dating: "It seems sort of ridiculous to be seriously dating someone in high school. I mean, what's the plan there? Continuing to date through college and then eventually get married? That seems sort of unrealistic."

Although the study did not look at people under 13, Twenge said she suspects the postponement of adult behavior begins in early childhood, starting with the decrease in children walking to school alone or playing unsupervised. In recent decades parents have become more restrictive about independent activities, and laws in some states have codified this, banning children from going out in public or staying home without adult accompaniment.

(Legislation has also delayed another adult activity: In the 1970s, the legal drinking age was as young as 18 in some states; it is now 21 almost universally.)

To Daniel Siegel, an adolescent psychiatrist and author of "Brainstorm: The Power and Purpose of the Teenage Brain," it makes sense that adolescents would "remodel" their brains to adapt to a society that has changed since the 19th century.

"In a culture that says, 'Okay, you're going to go to high school, go to college, go to graduate school and then get an internship, and you're not going to really be responsible till your late 20s,' well then the brain will respond accordingly," he said.

Whether the changes are positive or negative depends on the reasons for delaying adult activities, Siegel said.

If the delay is to make room for creative exploration and forming better social and emotional connections, it is a good thing. But "if it's fear-based," he said, "obviously that's a concern."

Among teenagers now, "there is a feeling you're getting of, 'Wow, the world is pretty serious, so why would I rush to immerse myself? . . . Why don't I stay with my friends and away from anything that has heavy consequences, like pregnancy or sexually transmitted diseases?' "

Teenagers are also more conscious now about the possible repercussions of their actions, said Stephanie Coontz, director of research at the Council on Contemporary Families.

"They're starting to realize, wow, they really do have to worry about their résumés," she said. "They come in without the kind of reckless disregard of consequence that a more confident generation of kids had, who said, 'I'll drop out of school and join the peace movement — what the hell?' "

With fewer career paths available to those without a college degree, Coontz said, young people can no longer afford that kind of nonchalance.

"They're absorbing the same kind of anxiety about the future that their parents have for them," she said.

Chiara Power, 15, of San Juan Island in Washington state has no interest in dating, driving, working for pay or drinking alcohol — and the rising costs of college keep her up at night.

"I'm already panicking and having nightmares about the student loans that I'll never escape, and I'm worried that I'm going to end up homeless," she said.

Her parents try to assuage her fears. "They're just like, 'Dude, that's not happening for the next three years, so chill.' I can't chill. I have no chill," she said. ". . . There's just so many people saying, 'Oh, it's going to be hard when you get out there.' "

Her mother, Penelope Haskew, 45, feels mixed about her daughter's preference for spending free time at home with her family.

"On the one hand, I know she's safe, she's not out getting pregnant or smoking pot or drinking or doing all kinds of risky stuff that I can imagine would be age appropriate," she said. But Haskew wonders whether her daughter is missing out on life lessons those behaviors can teach. "Is that stuff necessary for human development? Do you have to be risk-taking as a teenager in order to succeed as an adult?"

Still, she agreed with her daughter that the world seems more treacherous now than when she was a teen. "Climate change is super real, and it's obviously happening as we speak," she said. "Maybe the scary things about being an adult are so much more concrete right now that it's just safer to not become an adult."