"I think previous generations were more afraid to show affection to other males, because it was viewed as nonmasculine or something," Pasko said. "But bromance is in our common vernacular now, so I don't think people are too afraid of it anymore."
The rise in hugging can be directly traced to declines in homophobia, according to Mark McCormack, a University of Durham (England) sociologist who has studied the behavior of young men in the United States and the United Kingdom.
"These guys don't care whether other people perceive them as gay. In the '80s and '90s, if you were perceived as gay, you'd face huge stigma for it. You'd get marginalized and insulted," he said. Now, he says, "gender behavior isn't regulated in the same way."
In March, McCormack and colleague Eric Anderson of Winchester University published a study of British heterosexual college-age athletes. More than just hugging, 93 percent reported having "spooned" or cuddled with a male friend.
The research made waves in the international press - and the reaction to it made waves among McCormack's students.
"Older men are shocked that [this behavior] is happening, and younger men are shocked that it's noteworthy," he said.
McCormack said several types of gateway hugs are facilitating the shift.
Consider the drunken, I-love-you-man grip: Once men realize they're no longer being policed for such intoxicated behaviors, they might feel more comfortable hugging when sober.
It can kick off a "virtuous cycle" of hug proliferation - an arms race, if you will.
Other influences include the tactile traditions of team sports, known for encouraging swats on the butt and exuberant post-win pigpiles. Lately, even the NFL draft has become a hugfest: Each player gets a squeeze from commissioner Roger Goodell (although kissing on draft day, as gay player Michael Sam proved this year, remains controversial).
Yet another gateway is the widespread adoption of the hug-handshake hybrid (in which a handshake gets upgraded with a slap on the back) appropriated from African American culture and favored by President Obama - which caused a scandal for New Jersey Gov. Christie, who has denied hugging the president during Hurricane Sandy's aftermath.
While the man-hug is on the rise, Christie isn't the only guy fending off unwanted embraces.
Klint Kanopka, 31, an 11th-grade science teacher at Academy at Palumbo, a South Philadelphia public school, has noticed a trend among students: "They really like to hug each other a lot, and they also try to hug me."
It's happened frequently enough that he has developed a defensive stance: "I usually just leave my arms at my sides and say, 'Please don't touch me' or 'I don't like being hugged.' I just try to make the experience as awkward as possible for them, so they're not compelled to do it in the future."
Kanopka thinks increasingly informal American culture has made hugging more acceptable, but he's just not a hugger. Keeping peers at arms' length is also an ongoing project.
"I'll try to preempt [a hug] with a very formal handshake," he said. "If you're firm enough, you can lock your arm to force that distance. When they try to pull you in [for a hug], you can push."
Huntingdon Valley etiquette consultant Gail Madison said the subject is unavoidable when she's working with college students and millennials.
As they enter the workforce, she said, it can be problematic.
"A lot of women have been doing this for a long time, and that's inappropriate as well," she said.
She advises clients who wish to forestall an impending hug to take a sideways stance, leading with the right shoulder to offer a businesslike handshake.
Or, offer your hand but take a step backward to reclaim your personal space.
If all else fails, she said, plead the flu.
Madison said hugging the wrong person - say, a boss, potential client, or girlfriend's father - can come off as disrespectful or phony.
"It's a sign of familiarity that's inappropriate," she said. "We need to learn a more appropriate way, which is handshaking."
But even some boomers are hugging more these days. McCormack thinks that will only increase.
John Langan, 54, a marketing professional from Northeast Philadelphia, is, he admitted, "kind of a hugger."
But his protocol for embracing male friends differs from Pasko's bear hug: He goes for a quick, closed-fist squeeze. "You get in, you get out. You did your business, you're out of there."
Sociologist McCormack noted that studies had found that hugging has real health benefits, including increases in mood-elevating hormones like oxytocin and declines in blood pressure, heart disease, and depression.
Whatever the benefits, more are taking part. Minimum-wage activist Rafael Rivero, 28, of South Philadelphia, who is gay, said he had noticed that as rights issues - such as the legalization of same-sex marriage in Pennsylvania in May - become more visible, many men welcome a friendly embrace. But others do not.
"There are two divergent trends," he said. "Some people are more open to it, others it makes uncomfortable. You kind of have to feel the person out."