Much of modern human behavior, from sublime feats of creation to shocking acts of destruction, is measurably a legacy of our animal ancestors. Although our evolutionary relation to the higher apes has been well documented and widely appreciated, the beginnings of our behavioral story can be traced much further back in evolutionary time.

In this book, Robert Jay Russell opens the tale not with our apelike ancestors of 5 million years ago but - even closer to the roots of our primate family tree - with the lemurs of 50 million years ago.

Through Russell's thoughtful exposition of natural history and exploration of the emerging field of evolutionary psychology, which encompasses biology, evolutionary theory, anthropology, and paleontology, we gain new insights into our species and ourselves.

He shows how gender differences in various types of social behavior - courtship, bonding, mating, infant socialization, status-seeking, aggression, power-sharing - have come to us more or less intact through tens of millions of years of evolutionary history.

In what may prove a controversial discussion, Russell shows that language evolved to foster deceptive communication, and that monogamy, fatherhood, and the two-parent family are relatively recent, often troubled, social experiments. Human social experimentation continues, he claims, as females join male power groups, males act as single parents, and generations of children are socialized by television.

Russell contends that humans are a species of unprecedented social manipulators. With careful use of our power to reason and communicate - and with knowledge of our evolutionary psychology - we can build more satisfying personal relationships and better, less destructive societies. But the time to act is at hand. Russell notes that the disastrous and uniquely human legacy of overpopulation and habitat destruction may soon outpace our capacity to change.