Bob Dylan told baby boomers not to trust anyone over 30.
Now, the millennials, who comprise several generations, snarl "OK, Boomer" to us aging postwar babies.
The generational putdown, an Internet sensation, has received rebuttals from New York Times columnist Maureen Dowd and Chicago Tribune columnist Clarence Page.
Generations X, Y and Z - what will new generations be called now that the letters have run out? - blame us boomers for climate change, declining economic prospects, Donald Trump and the Eagles. They probably think Dylan can't sing.
Dylan and other Baby Boom heroes were not even Baby Boomers. Dylan, born in 1941, and John Lennon, in 1940, were of the "Silent Generation," which came after the "Greatest Generation," and before the post-war baby explosion. With all of their music and social protest, those rockers weren't very silent.
Once we sang "The Times They Are a Changin'." Now, the younger generation wants us gone. As college football old-timer Lee Corso would say, "hey, not so fast."
In the pre-industrial age, people lived pretty much the same year after year. The generations' experience stayed the same, and people died young. Retroactively, historians branded ages like the Renaissance and the Enlightenment, but Shakespeare, Michelangelo and Voltaire didn't think of themselves as members of defined generations.
Generational conflict goes back to ancient times. Ecclesiastes, in the passage from which Ernest Hemingway found the name for his novel "The Sun Also Rises," warned that "one generation passeth away, and another generation cometh; but the earth abideth forever."
Britain in the 19th century began identifying historical periods with the reigns of monarchs: the Victorian Age, the Georgian Age. Literary critics retroactively called Keats, Shelley, Wordsworth, Coleridge, Lord Byron and Charles Lamb the Romantics. Romanticism was also a European movement, including Beethoven and Goethe.
During the 20th century, enormous changes from decade to decade led to the rise of distinct generations. Those of the Depression Era had different outlooks from those born in the 1950s. Music, fashion, art, culture, and social mores shifted.
The designation of generations emerged after World War I, when Gertrude Stein told Hemingway that he and his contemporaries were members of a "Lost Generation." Then came the postwar flowering of writers like John Updike, Truman Capote, Robert Lowell and Gore Vidal. New waves of writers, musicians and film stars followed. From Chuck Berry to Katy Perry, the world kept turning.
The Baby Boomers reached a new level of self-consciousness, or bloated self-importance. Talking about my generation, we did bang the drum and blow the horn quite loudly.
Now, the millennials look at us as old duffers.
But remember, kids, a new crop of babies is being born, who will look at you as hopeless.