Clinical psychologist William Pollack, the author of Real Boys and the codirector of the Centers for Men and Young Men at McLean Hospital at Harvard Medical School, says that fathers can actually be scared when they first come into contact with such filial unruliness. "The more sensitive the male, the more frightened they are," he explains. "They're afraid the boy's going to be a bully or a school shooter. . . . Or they have the fear that they won't be able to relate to their sons—that they won't be able to be buddies."

Would a buddy, after all, hammer the stereo with a rubber stegosaurus every time you try to introduce him to the delicate charms of Nick Drake's Pink Moon? Psychologist Michael Thompson, the author of Raising Cain and an expert on the behavior of boys, tells a story about a friend of his, a librettist working in musical theater, who found out that his son wanted to go to Madison Square Garden to see professional wrestling. The father, Thompson says, "was completely bewildered."

This past fall Matt Goldman, one of the three cofounders of the Blue Man Group, the experimental performance troupe, helped launch the Blue Man Creativity Center, a preschool in downtown Manhattan where kids can frolic in the sort of rampant whimsy that has made the blue dudes famous. There's a Room of Wonder, where giant animated fireflies dangle from the ceiling and kids splash the walls with glowing black-light paint, and a "texture pit," as Goldman calls it, "that has all these soft and velvety cushions that they bury each other in." In spite of Goldman's inclinations toward touchy-feeliness, his own 4-year-old son has a fondness for stomping on stuffed animals and unleashing the beast in pillow fights. "It answers a lot of the nature/nurture questions, because I definitely did not introduce this behavior to him," Goldman says. "I read a great study where they took four toddler chimpanzees and put them in a room with a bunch of toys. The boy chimps played primarily with the trucks and the guns. You know, it's baked in there."

But now, apparently, men have been so successful at suppressing their cooked-in testosterone that they need a manual in order to teach their sons some of the rites of passage that used to be passed down from one generation to the next. Consider the phenomenal, nipping-at-Harry Potter's-heels popularity of Conn and Hal Iggulden's The Dangerous Book for Boys, an encyclopedia of get-your-hands-dirty adventure that you can imagine Sir Ernest Shackleton passing along to his progeny so that they'd never forget how to skip a stone, shoot a bow and arrow, or stay alive on a journey to the South Pole. "In this age of video games and cell phones," the brothers announce in the introduction, "there must still be a place for knots, tree houses, and stories of incredible courage." Not coincidentally, Pollack points out, the Boy Scouts were formed in England at the turn of the 20th century because of a widespread concern that British men were becoming feminized. "They were having a renaissance in England of men who read books and became literary and were starting to go to salons," he says, "so people felt they had to go outdoors and be rugged."