The first-ever Human Be-in turns 40

Their hair, once a symbol of youthful rebellion, is now shot through with grey. Bodies that writhed with wild abandon to psychedelic music sport stiff knees and wrinkles.

"How many of you are on acid right now?" rock critic Joel Selvin asked an audience of former hippies who turned out yesterday to mark the 40th anniversary of the Human Be-in, the counterculture event that set the stage for the Summer of Love. "How many of you are on antacid right now? "

In many ways, the '60s were born on 14 January, 1967 when musicians, poets, visionaries, student radicals and wayward youth gathered in Golden Gate Park.

Those who were there agree that neither they nor San Francisco have been the same since. Part rock concert, part protest, part literary festival, the Human Be-in was billed at the time as a "Gathering of the Tribes" meant to unite and stir up the various wings of the counterculture movement.

Estimates of the number of people who cavorted on the park's Polo Fields that day range from 10,000 to 50,000.

The speakers and bands who appeared reads like a "Who's Who" of 1960s icons: LSD advocate Timothy Leary, poets Allen Ginsberg and Gary Snyder, comedian Dick Gregory, the Grateful Dead, Jefferson Airplane.