Why Don't We Dance Anymore? When a dance move is born, the air is heavy with promise. Think of Chubby Checker, doing the twist with casual grace on "American Bandstand." Think of that first surreal nightclub scene in "Sweet Charity," in which Shirley MacLaine's young dancehall hostess is mesmerized by a troop of dancers serving Bob Fosse's unique style of über-mod gesticulation. Think of Jennifer Beals's solo audition in "Flashdance," the movie that led to a million ripped sweatshirts. Think of Michael Jackson's first moonwalk. Within seconds of observing a dance move's birth, the amateur masses begin to work to replicate it. In the old days, this meant packs of junior-high-school kids trying to moonwalk in the hallways after seeing "Billie Jean" play on MTV, or imitating Kevin Bacon's jerky hop-kick whenever the song "Footloose" came on at the eighth-grade dance. Today, the dance-move testing site is YouTube, where brave souls can be observed by the world trying to Dougie or do the stanky leg in their native habitats. Instead of trickling downward - starting in Hollywood and spreading to the masses - most of today's dance moves, like bone breaking or the Soulja Boy, trickle upward. They come from the streets and are disseminated via YouTube, one Harlem Shake at a time. Professional spies discover What the Young Kids Are Into These Days and incorporate that raw genetic material into the routines for Lady Gaga's or Drake's multicity tour. Choreographers are hired, and they train professional dancers to execute the move until it's far more finely calibrated and expertly performed than originally intended - maybe too much, like watching a fuzzy old film that has been digitally remastered for an HDTV. At which point the sterile, fast-moving troops that flank stars like Beyoncé get into the act, transforming each organic, soulful move into something that looks like C.G.I. Soon you can spot, say, a pair of guys in yellow jumpsuits busting hip-hop moves to honor "Breaking Bad" at the Emmys, or the manic teenagers of "Glee" popping and locking at show-choir regionals. That's when the dance move starts to show clear signs of mutation. Soon, this new strain of the dance seeps back into the cultural groundwater, poisoning the wider environment. Competitive high-school cheerleading squads integrate the move into their routines, to inject a little flair right after the giant pyramid with the celebratory human bodies shooting off the top. The dance move is further battered by those massive dance brigades at the Super Bowl, who insert the move into a prominent spot in the halftime show. Next the choreographers from "So You Think You Can Dance" resolve to tastefully conquer the new move, and local dance instructors incorporate it into their weekly fitness classes. "Like Zumba, but with a better core workout!" Wedding D.J."s get into the mix, rallying rooms full of intoxicated humans to try maneuvers that will be emblazoned on the brains of their extended families forevermore. Later, the dance move arrives on cruise ships like a virulent infection, flourishing in a microcosm packed with the sorts of people who relish doing the Macarena en masse. Finally the dance move settles in awkwardly at the local senior center's exercise class, where a room full of baffled seniors find themselves reluctantly Twerkin" to the Oldies. "When you dance, you can enjoy the luxury of being you," the Brazilian author Paulo Coelho once wrote. A kind of luxurious self-satisfaction is clearly present when my 6-year-old daughter and her friends dance to Pink's "Try" and Kelly Clarkson's "Stronger" in our family room. It's mesmerizing to witness raw, puppy-dog enthusiasm combined with loosely organized, flailing limbs. Sharp elbows fly, hips waggle, styles and eras and dance crazes gleefully collide as the "Gangnam Style" horse dance segues into "Saturday Night Fever" disco pointing. Odd-looking twirls result in multi-kid pileups, and everyone shouts about whether the lights should be on or off (or should flicker on and off, as they do at real dance clubs).