Fascinating work by Forrest Wickman in Slate:

Toward the beginning of the 2012 comedy 21 Jump Street, Officer Jenko (Channing Tatum), a onetime cool kid, gives his partner some advice as they prepare to infiltrate the ranks of the cool kids at Sagan High. “You gotta one-strap it,” Jenko chides Officer Schmidt (Jonah Hill). Schmidt, a onetime nerd, is two-strapping—wearing his backpack over both shoulders. That is not, warns Jenko, what cool kids do.

This advice may sound obvious to all cool kids of a certain age, but when the officers make their debut at school, times have changed. Jenko’s attitude—“I don’t care about anything,” he announces—has gone out of style. The cool kids are into diversity, environmentalism, and, worst of all, trying. And symbolizing this generational sea change: “Everybody’s two-strapping it,” notes Schmidt.

When I first watched this scene, I thought: Funny bit, but is it right? I, like everyone cool (or trying to be cool) in my high school, one-strapped all the way. It was a foundational tenet of cool—you might argue about what kind of music was cool, or what clothes, or what hairstyles, but it was a given that one-strapping was the only way to wear a backpack. Is one-strapping really not cool anymore? And if so, how could something once so cool become so not? My search for the answer sent me on a quest in which I’d consult pediatric orthopedic surgeons, re-examine decades of pop culture, and track down the one consummately cool high-schooler from East Amherst, N.Y., who might have the answer.