98% Monkey and 2% Man : THE THIRD CHIMPANZEE: The Evolution and Future of the Human Animal <i> By Jared Diamond</i> , <i> (HarperCollins: $25; 304 pp.) </i>

Judges still tell people who batter children and wantonly defile the helpless that they have “acted like animals.” There remain large numbers of people in science-based countries such as ours who do not accept the theory of evolution. Even in the university, the intellectual and administrative gap between the natural and the social sciences continues to permit practitioners of the latter largely to ignore the work of the former.

It remains a striking problem that it is possible to acquire an advanced degree in nearly all the social sciences without knowing either the biological theories that underlie our knowledge of the behavior of other animals or the subtlety and detail of their societies. Indeed, the gaseous indeterminacy surrounding deconstructionism and other such fashionable obfuscations has encouraged influential members of social sciences such as mine, anthropology, to claim confidently that it is not possible to know firmly what the reality of human behavior is because everything is just a text, just a version, just a social construction--just one thing or just another.

At the same time, the biological sciences, from the discovery of DNA on, have yielded a wonderful and burgeoning array of insights into both the extraordinary complexity of natural patterns in physical and social life and also the ever-deepening antiquity of the human line. Just last month, for example, a Yale paleoanthropologist argued persuasively for adding another 600,000 years to our human lineage. This means that our boatload of Mayflower pre-hominids began to settle the human race more than 2 million years ago.

Those years have left their mark on our bodies and on our behavior--but less of one than we might expect given the vast arch of evolutionary time. In this richly informed exploration of human behavior and its evolution, UCLA medical school physiologist Jared Diamond describes how we are, along with the pygmy chimp of Zaire and the common chimp inhabiting the rest of Africa, the third species of chimpanzee. We share more than 98% of our genetic program with these relatives, and his case is sturdy indeed that even if the 2% differential is clearly, vitally and elaborately influential, nonetheless we have to know about the other 98% if we are to adapt Socrates’ advice to the whole shebang: “Know ourselves.”

Diamond brings to his work not only the shrewd practicality of a sophisticated physiologist but also the curiosity and color of a field worker who has explored New Guinea, coming to know the behavior of its birds as well as the lives and intriguing language of its people. He has a clear sense of how to advance his evolutionary arguments through lively examples.

An eager and learned explorer of matters ranging from art and language to adultery and the evolutionary role of horses and viruses, Diamond offers a wealth of useful information about serious matters, presented in a clear and interesting if occasionally over-earnest style. He shows unsentimentally that preindustrial and even pre-agricultural people could be as profligate and destructive about the natural environment as the most callous modern skimmer of the rain forest. He is particularly enlightening on the subject of the biology of race, and if anyone who has sauntered through these pages still believes that race is anything other than skin-deep, he should go back to reading school.

At the same time, Diamond provides an original and thoughtful discussion of why races emerged (relatively recently). He concludes with Darwin that they resulted not from natural selection but from sexual selection--from, in other words, a human’s decision to choose a mate on aesthetic or other criteria. Sexual attractiveness among members of the incipient racial groups was principally responsible for finally generating racial differences in appearance, not functional practicalities such as the need to throw off body heat or to respond to climate. This point is particularly important to stress in this weird period of intellectual history, where fulsome ideological claims are made that race is at once both wholly irrelevant and coercively determinative. It’s neither. Finally, it’s mainly about looks.

Diamond explores two central themes with grace and force, albeit with some undue innocence and a vague aroma of political correctness. He describes how our species has murderous capacities and is willing to explore in dolorous detail war and genocide in all their grimness without leaping piously to identify as wholly responsible the hooded bad guys from Wall Street or the Politburo or wherever: He is painfully aware that we are all the bad guys. Since the first step in solving any problem is identifying it clinically, his essay on this contentious subject is especially useful.

Therefore it is too bad he fails to acknowledge that he is here a Jared-come-lately inasmuch as a much earlier assertion of this kind--Robert Ardrey’s (astonishingly synthetic and prescient if exaggerated) “African Genesis” of 1961(!)--showed both the African origin of humankind and its frailty as far as bellicosity is concerned. Similarly, Diamond’s well-argued case that agriculture was just a great human mistake that people seek to overcome as soon as they can get to Paree was made more than 20 years ago by Robin Fox and me in our book “The Imperial Animal.”

There is no fair reason for Diamond to have overlooked or, in the case of Ardrey, scorned these and other earlier works. Perhaps this is because they were once seen as controversial and maybe are still. But the compassion and intricacy of “The Third Chimpanzee” suffers from an unnecessary sense of surprised discovery in areas in which others have worked before and with some success, though admittedly with less empirical and theoretical support than is now available to Diamond. It is also possible that because Diamond suffered some complacency about the range and depth of his material and his treatment of it, we’ve been given a less ambitious, grainy and risk-taking portrait of the third chimpanzee than the subject warrants.

As the song said, “it takes a worried man to sing a worried song,” and too little of this book is the lowdown blues. Nevertheless what is vital is that “The Third Chimpanzee” makes us take a searching look in the mirror that will be as unsettling to some as it will be enlightening to many.

There is a real struggle going on between scientists who embrace the force and provocation of evolutionary theory and other commentators who are happily content to describe just what is in front of their eyes and who are contemptuous of the implication of the Nobel geneticist Jacques Monod’s haunting assertion, “ Tout etre vivant est aussi un fossile” (Everything that lives is also a fossil). Diamond has provided an intriguing and rich sketch of the history of one fossil, us. He joins a lineage of skillful people at once skeptical and passionate about human nature and the possibility of understanding it.