Most of us have a few choice things to say about the problems we imagine are caused by testosterone. Robert Sapolsky, a Stanford University biologist and essayist, has gone a step further. In his well-crafted collection of essays, The Trouble With Testosterone, Sapolsky writes wittily and concisely about the biological basis of human behavior.

The book comprises 18 essays that explore the human condition by way of human and primate biology. Many are based on Sapolsky's field observations of wild baboons in the Serengeti of East Africa, while others are based on his laboratory work in the neuroscience department of Stanford. Overall, Sapolsky manages to make graceful connections between the field and the test tube without ever seeming pompous. He is rarely seduced by the hubris of science, and many of his essays demonstrate the discipline's shortcomings while praising its discoveries.

At times Sapolsky takes what seems like an obvious assumption and pleasantly shows us what we missed. In the title essay, for example, "The Trouble with Testosterone: Will Boys Just Be Boys," he takes a commonly held belief - that testosterone levels drive male aggression - and shows that it is simply not so. Instead, the opposite is true: Aggressive behavior elevates testosterone levels within a group of males. This conclusion is drawn by correlating the results of behavioral and biochemical studies. He maintains, however, that scientists have had a lot of trouble accepting this conclusion, partly because they view the study of behavior as somehow less scientific than the study of biochemistry. Measuring hormonal levels, he states, requires "a gazillion-dollar machine, you muck around with radiation and chemicals, wear a lab coat, maybe even goggles - the whole nine yards. Which toys would you rather get for Christmas?" Because this approach is more reductive, he writes, scientists hold a strong bias toward it, believing it to be more scientific, more correct. This, Sapolsky maintains, is a classic case of physics envy:

In his wry way Sapolsky goes on to explain that while you need some testosterone for aggressive behavior to take place, the hormone itself does not cause increased occurrences of aggression. But Sapolsky believes that by being blinkered to the obvious, scientists have sometimes hindered their understanding of this and other phenomenonas.

The scientist/essayist writes knowledgeably about the androgen testosterone here, but it is his own work on the stress-related glucocorticoids that provides a basis for other essays, including "The Young and the Reckless." In this piece, Sapolsky notes the common mammalian practice whereby young adolescent males leave their home troop for a new one. This transfer is often marked by great stress as the young male faces challenges in a new and dangerous environment. In particular, Sapolsky tells the story of Hobbes, a young male baboon who defied the hierarchy and ascended quickly within his new troop. While Hobbes's behavior caused great stress among members of his adopted troop, it produced even greater stress - as indicated by high levels of cortisol, a glucocorticoid, and low levels of white blood cells - for him. It seems that whether a young ape is dominant or subservient in the hierarchy doesn't matter: he becomes stressed out either way. The question, therefore, is why young primate males continue to risk life and limb for adventure when it is clearly bad for their health. Alas, not even Sapolsky has the answer to that.

The author, who has been the recipient of a MacArthur Fellowship and an Alfred P. Sloan Fellowship, among other awards, manages to spin good yarns out of the most improbable subject matter. In "Poverty's Remains," he points out that because the cadavers studied in medical schools have historically come predominantly from the poor, much of what was thought to be normal in the human body has since been discovered to be the abnormal response to a lifetime of hardship and stress.

Sapolsky gives a poignant example of how this medical misunderstanding can have grave consequences. In the latter days of the nineteenth century a pathologist named Paltauf systematically autopsied babies who had died of sudden infant death syndrome (SIDS). Paltauf found that the babies had what seemed to him to be abnormally large thymus glands. But what he was seeing, when compared to infants who had died of other stress-related causes, were, in fact, normal-size glands. Recognition of this "disorder" led to a treatment for SIDS prevention - irradiation of the thymus - that did nothing to prevent SIDS. Tragically, many healthy children who underwent this treatment developed thyroid cancer from the unnecessary radiation.

In his final essay, "Circling the Blanket for God," Sapolsky makes a compelling argument linking schizophrenia-type behavior and the voices heard by the forefathers of our religions. He also draws a parallel between obsessive-compulsive behavior and the minutia of religious rituals.

A couple of the essays seem a little strained, but for the most part Sapolsky makes his points deftly and with humor. He writes in a straightforward style, without belaboring his points, in language that is simple and understandable to someone with very little science background, while the subject matter would not bore readers with scientific training. At the end of each chapter, Sapolsky gives several references for further reading; many of them citing his own work in scientific journals. The essays, however, originally appeared in Discover magazine and The Sciences. They have been edited here into one fresh, compelling, and thoroughly readable volume.