THE HIGHEST manifestations of human intelligence have always been represented by a fusion of philosophy and science. In the modern world, the honor roll for such efforts includes names like Albert Einstein, Erwin Schroedinger, Alfred North Whitehead, Harlow Shapley, Loren Eisley, Leo Szilard, Karl Menninger, Teilhard de Chardin, and Lewis Thomas. Their ideas about the physical and biochemical nature of human beings have enriched speculations not just about the meaning of life but about the possibilities of human existence.

The particular part of this forest that engages Melvin Konner's attention is human evolution in the light of contemporary knowledge. He provides a guided tour of what he believes are the significant findings of researchers in a wide variety of fields ranging from anthropology to genetics and endocrinology. His running commentary is lucid, appealing, well-integrated. He makes no attempt to conceal his own excitement but his voice is steady enough to maintain sequential command of his material. The result is a thoroughly engaging adventure of ideas on the human condition.

This is not to say that the book is totally without bias. Konner has a pronounced tilt towards the geneticists. For example, he leans very heavily on animal studies to refute the views of behaviorists, exposing himself to the criticism that there are elements of uniqueness in human beings that limit the usefulness of such findings. In another connection, he refers to the demonstrations of Seymour Kety, of Stanford and Harvard, showing that schizophrenia is partly genetic in basis. The question here is not whether this research is accurate -- there can be little doubt that it is -- but whether the reference is totally pertinent to Konner's position. There is hardly an institution for the mentally ill that does not house people who became "schizophrenics" -- the term resists scientific definition -- largely as the result of environmental or behavioral situations. A substantial number of cases have been documented involving young women who took heavy doses of amphetamines for purposes of severe weight reduction and who developed pellagra psychoses with hallucinations that led to the mistaken diagnoses of schizophrenia. They were committed to mental institutions, treated as schizophrenics, cut off from their parents, and became in fact what they were mis-diagnosed to be.

Konner would probably say that this proves his case, contending that these particular young women were genetically susceptible. He may be right, but that doesn't disprove the fact that mental illness can sometimes have predominant circumstantial origins. There is a point at which the conditions of human existence, like the saw cutting off the finger, creates an effect that cannot be explained by genetic factors alone. In any case, nothing is more futile than attempting to debate the question of heredity vs. environment; they tend to interact in varying degrees.

Recent brain research assigns a larger role to the biochemical effects of free will and the emotions as a whole than seemed possible only a few years ago. Since the emotions originate in the brain, Konner would probably contend that the primary factors are genetic in any case. Yet this view does not dispose of the matter. Current brain research is demonstrating that different attitudes can activate different brain secretions. Indeed, a theory is gaining ground, with Richard Bergland of Harvard as one of its most prominent proponents, that the brain is not just the seat of consciousness but a gland -- probably the most prolific gland in the human body.

Unless I am mistaken, many readers will come away from Konner's book with a more robust view of human prospects than he himself appears to hold. For the wide array of research materials he has assembled would appear to support a far higher estimate of human capability than his own conclusions seem to accept. He uses the word "doubt" as being most descriptive of his feelings about the human future. "If you ask me," he writes, "how to set your sail in the storm of claim and counterclaim, of fact and lie and theory, of warning and prophecy and judgment and exhortation, I do have a bit of advice that I earnestly believe in, which can be summarized in the one-word injunction, Doubt."

I can understand how any serious-thinking person, confronted with the full inventory of the perils and challenges confronting the human species in a nuclear age, will be oppressed by doubts, even despair. But we must not confuse biology with politics. We should not underestimate the depth or the severity of the dangers surrounding us, but neither should we under-estimate our capacities for dealing with them. Our strong belief in these capacities is a vital part of the process of challenge and response, to use Toynbee's celebrated phrase.

Konner's subtitle refers to "biological constraints on the human spirit." There is at least as much evidence to indicate that the reverse is true; the human spirit can help surmount our biological limitations. The moon journey was only one such example. What makes human beings unique is their ability to do something for the first time.

I must not allow these reflections to obscure my high admiration for this book. Melvin Konner has furnished us with rich materials for self-understanding and, what is more important, for speculation about the unfinished species to which we belong and have the obligation to sustain. Certainly, I have no difficulty in agreeing with his closing words:

"It is for us, much more than for any previous generation, to become serious about the human future, and to make choices that will be weighed not in a decade or a century but in the balances of geological time."