The family is humanity's oldest and most universal institution. But its shape, size, aims and ideologies seem infinitely variable. Japan's families down the ages have been polygamous and monogamous, multigeneration and single-generation, swarming with children or comparatively, if not entirely, devoid of them.

Through vast changes over vast stretches of time, the family has transmuted but endured. It was sacred. One didn't argue whether it was a good thing or a bad thing, whether it worked or not; it simply was. The wonder is that now, when no thing simply is, when everything is open to question, the family as an institution survives. Will it indefinitely?

It faces two main challenges. The first is the need for, and a felt entitlement to, self-fulfillment. Are mating, procreating and assuming responsibility for offspring the best of what life has to offer? Maybe an unmarried life of unfettered freedom offers broader horizons? That many Japanese have come to think so is suggested by a swelling pool of lifetime singles.