It happens. If you live past 30, one day you wake up and and ask the metaphysical equivalent of: Is it soup yet? Am I middle-aged? Me?
The concept of middle age has always been a muddle. Now, as the baby boom marches through it, middle aging becomes a topic of momentous demographic, economic and social importance.
One has even compared it, in historic significance, to the closing of the frontier. Clearly, there are more and more people out there looking like Wallace Shawn and fewer looking like Johnny Depp.
Whether it is generational narcissism or high time to explode the myths about midlife, biologists, psychologists, mythologists and the mob of people turning 40 are beginning to rethink middle age.
As a result, expect an avalanche of research.
Projects such as the MacArthur Foundation-funded Research Network on Successful Midlife Development will spend the next seven years answering such basic questions as: What is midlife? Is it a crisis, a transition or a cruel joke?
Expect to be bombarded with exercise and nutrition programs such as that described in William Evans' new book, "Biomarkers."
Mr. Evans worked with 90-year-olds first starting to exercise and found "they tripled their strength and increased the size of their muscles just like 20-year-olds." The message is clear to the aging and the middle aging: It's never too late. Move it.
Expect a plethora of books to empower us, like Ross Goldstein's "fortysomething: Claiming the Power and the Passion of Your Midlife Years." Dr. Goldstein, a psychologist, tries to help his clients distinguish between "healthy denial vs. unhealthy denial."
He characterizes midlife by the question, "Should I settle in and accept the indignities and boredom of my job or should I follow my bliss?"
If the 40th birthday, the big Four-O, has become an occasion for desperate partying, a kind of baby boomer bar mitzvah, the 50th looms as a mock wake.
Author Arthur Naiman wrote on the invitation to his birthday party: "Join me as I celebrate (?) my 50th birthday and try to wrest a few last wretched glimmers of daylight from the encroaching flood tide of decrepitude, senility and . . . I forget what the third one was."
Yet Mr. Naiman feels the worst of middle aging is behind him.
"It hit me in my late 30s. I began to panic. I felt I'd done nothing in my life to make my mark," says Mr. Naiman, even though by then he'd been a teacher, a copywriter, a photographer, an abstract-expressionist painter and cartographer of the city of Berkeley.
At 39, Mr. Naiman embarked on a new writing career with a humorous reference book, "Every Goy's Guide to Common Jewish Expressions." In 1987, he started his own company and co-wrote and published "The Macintosh Bible," which sold 500,000 copies, making it one of the best-selling computer books ever.
Despite such tales of midlife triumph, biologists tell us there is no reason for us to live past 30.
"Thirty years is sufficient time for humans to produce new progeny and to rear that progeny to sexual maturity," says Leonard Hayflick, in the vernacular verite of the cellular biologist.
"We are in the Stone Age of understanding aging," says Mr. Hayflick, who is on leave from his professorship at the University of California at San Francisco to work on his own book about the biology of aging.
He explains that for most of time the human species has had a life expectancy closer to 18 than the current 75. "There is no concept of middle age in wild animals," he says, observing that if animals experienced the kind of slowing down common to middle-age people they'd become easy prey.