Joshua Glenn, the brains behind Boston Globe blog Brainiac, has written a fascinating essay on U.S. generations — you know, like the Boomers and Generation X, two groups who considered themselves the most futuristic and modern types around. But Glenn argues that there are a lot of hidden generations that haven't gotten much play despite their influence in the twentieth century, like the Anti-Anti-Utopian generation right before the Boomers. Among his picks for influential Anti-Antis are Muppets creator Jim Henson and scifi great Samuel Delaney. [Brainiac]