Social anthropologist Montagu's latest work is a celebration of neoteny as the guiding principle of human evolution. Neoteny, a term that Montagu uses interchangeably with paedomorphosis, is the theory that a species can undergo rapid evolutionary change as a result of the retention of fetal or juvenile traits in sexually mature adults. Good old fiat-faced, small-jawed, relatively hairless Homo sapiens looks a lot more like an infant or jufenile chimp than like the chimp's parents. Montagu (in common with Stephen Jay Gould) modifies the definition of neoteny by adding that human adults also look more like their own youthful counterparts--children and adolescents. In contrast, gorillas and chimpanzees tend toward gerontomorphism: as they age, the apes' jaws protrude more, their brow-ridges grow, their teeth get bigger. Montagu cares less about physical traits, however, than about behavior. The retardation of development that neoteny implies underlies the vast plasticity of human development--the years of nurturance, curiosity, exploration, educability. Here lies the clue to the human success story. And, Montagu warns, we are in danger of losing sight of those neotenist traits through rigid school systems and cultural mores that restrict horizons and demand that children grow up quickly. So a good part of the book is social prescription. Montagu preaches a fine idealistic line about the need for schools that would encourage interchange among successive grades in a cooperative, supportive setting. At the other end of the scale, he worries about ""agism""--the rampant prejudices, fears, and myths that lead to discrimination against the elderly. Here, he cites current and good research on brain changes in aging which debunks the idea that you lose all those little gray cells and pass rapidly into senility. What you need is stimulation and exercise of mind to achieve that ""best that's yet to come."" Montagu's points are well taken--if only he didn't make them so often and so breathlessly. If only, too, he didn't devote so much space to the rightness or wrongness of pioneer neoteny thinkers like Louis Bolk. Still, even Montagu's excesses have their proven (and undeniable, charms.