Eva Horvath-Papp/Shanghaiereducation

In a reversal of Footloose, the young people are telling the old people to be quiet. Crowds of dancing retirees have recently become a common sight in China’s urban squares, as guang chang wu, a type of organized group dancing, has taken over the country’s public spaces. Most enthusiasts are dama, or older women, who crave social interaction and exercise. But the round-the-clock hours they keep, and their blaring pop music, are prompting vitriol from fellow city dwellers. My father’s wife, who is in her 30s, recently found herself screaming obscenities at a group of very noisy seniors who had taken to dancing outside her apartment in Guangzhou.

Some enraged bystanders have hurled garbage and excrement at the dancers. Others have taken to Weibo, the Chinese Twitter, to denigrate guang chang wu grannies and grandpas in shocking language. Some insults riff on a popular dance move, a zombie jump inspired by Michael Jackson’s “Thriller” video; one detractor likened the dancers to “a group of walking dead.” Another observer lambasted the revelers for “showing off their shriveled breasts.”

This reversal of the customary Chinese reverence for elders is startling. The country’s seniors have always taken to public spaces to socialize: tai chi in the morning, pai gow and mah-jongg in the afternoon. But this new pastime is much louder than the old ones, and it arrives as runaway urban growth is tearing down the scaffolding of the traditional filial system—and as millions of aging citizens are poised to need support from younger people.

Not that the oldsters seem, for the moment, particularly helpless: In October, a young man was sentenced to prison for trying to rob a jewelry store near Shanghai. Although he’d brandished a kitchen knife as he entered the store, he was tackled by a dama twice his age. Her son, the store owner, informed the local paper that she was an avid practitioner of guang chang wu.

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