Origins: a skeptic's guide to the creation of life on earth.

Origins: A Skeptic's Guide to the Creation of Life on Earth.

Robert Shapiro. Summit, $17.95. Scientific accounts of the origin of life have been called the achilles' heel of evolutionary biology: an inviting target for the attacks of Creationists. Science can describe the evolutionary path leading from an ancestral cell to a human being with more certainty than it can the development of the first cell from inert matter. To the skeptical eye of Shapiro, a biochemist at New York University, those explanations that have been offered look more like mythology than like science.

Textbooks and popular accounts suggest that life arose from a primordial soup, a thin broth of simple organic compounds formed by the action of lightning or sunlight on a primitive atmosphere rich in ammonia, methane, and hydrogen. The hypothesis owes its ascendancy largely to a 1952 experiment in which an electric spark discharging in a simulated primitive atmosphere generated several amino acids, the building blocks of proteins.

Geochemists no longer believe that the primitive atmosphere contained the right gases, and biochemists doubt that the amino acids would have survived in a primeval ocean. Moreover, Shapiro argues, the soup doesn't get you very far: the chance that a complex molecule such as a protein or DNA will spontaneously assemble in a dilute solution of simple building blocks is vanishingly small. Yet, in one form or another, the primor-dial-soup hypothesis remains the orthodox view. Why?

Shapiro points to what he calls a "predestinist bias' among students of the origin of life: an almost religious sense that "the laws of the universe contain a built-in bias that favors the production of the chemicals vital to biochemistry and ultimately to human life itself.' Crude, probably irrelevant demonstrations like the 1952 experiment are convincing to people who are already disposed to believe that the chemistry of the universe and thus that of the early earth tended inevitably toward the generation of life.

Shapiro dissects related hypotheses, which place the origin of life in cloud droplets or hot springs on the ocean floor and specify the first living stuff variously as protein or DNA or RNA, and finds the same bias at work. He also examines, with varying degrees of sympathy, several very different proposals, including suggestions that the first living things were crystals of clay or that life on earth had an extraterrestrial origin.

The debate, as Shapiro presents it, is rife with speculations presented too forcefully, with inconclusive data put forward as definitive evidence and with explanations that look very much like Creation myths. It is no wonder that actual Creationists, who advance their own claims by seizing on inconsistencies in genuine science, have found an easy mark here. "As a group who themselves have attempted to pass off mythology as science, they can readily identify rivals who are attempting, even if unconsciously, the same substitution.'

Shapiro sometimes loses track of his argument in thickets of technical detail, and like anyone who sets out to debunk, he can get to sound smug. Even so, he gives a fascinating tour of the scholarly scene and a worthwhile lesson in the meaning of science.