Review

To be a well-informed citizen as the 20th century draws to a close is no easy mission. The expanding web of information and the escalating rate of specialization threaten to undermine the ideals of generalized knowledge and civilized discourse.

Will the adage "knowledge is power" be replaced by "information is chaos"? In the case of biology, David and Ilona Barash have answered that question with a remarkable affirmation of skillful scientific analysis and delightful, comprehensible literary style in The Mammal in the Mirror.

The authors describe their book as a "primer of bioliteracy." Their aim is to promote a realization of the "connectedness" of Homo sapiens to the rest of the natural world by demonstrating the "mammalhood" of human beings, from their genetic code to the way that they project their genes into the future through reproduction.

David and Ilona Barash bring an impressive array of complementary talents to their challenging task. David Barash is an accomplished writer on a wide range of topics ranging from sociobiology to nuclear disarmament. He has a Ph.D. in zoology and teaches psychology at the University of Washington. His daughter, Ilona, is currently studying for a doctorate at the University of California at San Diego, and has written a major article on the hormone leptin.

The Barashes' grand tour of human biology begins by ascending the "spiral staircase" of DNA. The authors analyze the components of a human DNA molecule, noting that it has an average of 3 billion nucleotides - the links in the spiral chain - compared to the 5 million possessed by an E. coli bacterium. This tremendous concentration of molecular information is stored in the chromosomes, each of which is organized "into a substructure that is yet more complex and dense than the DNA molecule itself."

A DNA molecule is a masterpiece of miniaturization. Occupying only a fraction of the human cell, DNA is the key to our lives. But DNA does not elevate human beings to a special status, because DNA is the common thread of all of creation. The authors note that some amphibians and plants possess more DNA than do humans. The key element in the DNA equation is not quantity but quality: the unique organization of "useful" DNA for each species into the "packaging units" that are their genes.

Human beings share close to "90 percent of their DNA with the rest of the living world, and approximately 99 percent with our closest nonhuman relatives, the chimpanzees." This fact makes for a rather tenuous human claim to star billing on the great chain of being. It is clear after reading Mammal in the Mirror, however, that we have a very special role in safeguarding the biodiversity of the world in which we live.

A breathless summary like this may give the false impression that Mammal in the Mirror is merely a recycling of high-school textbooks and newspaper clippings. Complexity is delicately interwoven into the book's generalized treatment of the DNA/RNA relationship, the nature of the cell cycle, and the working of the immune system. Later chapters widen the focus to study the process of natural selection and the exponential growth of the human population.

The ability of the authors to present complicated molecular processes in coherent, enjoyable prose is particularly well expressed in their discussion of the molecule adenosine triphosphate (ATP). ATP is produced by mitochondria during the basic process of cellular respiration. Oxygen is used by the mitochondria to produce the energy-rich ATP from larger food molecules such as glucose. The waste product from this transaction, carbon dioxide, is then released when we exhale.

In a memorable passage, the authors use the analogy of a vending machine to elucidate the role of ATP in this energy synthesis. Think of food molecules, they write, as being hundred-dollar bills that need to be changed into smaller coins for energy to reach our cells. These "handy pieces of pocket change" are ATP. "What the U.S. dollar is to international finance - or the quarter is to vending machines in the United States - ATP is to the personal economy of nearly every living thing."

The later chapters, which deal with ecology, evolution, and sociobiology, are more polemical in tone. The authors address controversial topics such as the threat of industrial development to animal habitat, population growth and birth control, and the continuing opposition of religious groups to the theory of natural selection. They categorize opposition to evolution, and therefore to a sense of kinship with nature, as biophobia. This aversion to the natural world is more than a fear of animals. Rather, it is based on a perception of nature as a "subtle psychic threat to our self-image."

Despite an occasional lapse into editorial commentary, the authors mount a cogent and disciplined defense of humanity's evolutionary roots. They brilliantly use the famous case of the change in color of moths in Great Britain during the Industrial Revolution to show that natural selection is not an unobserved, unproven theory. And they demonstrate that many of the anatomical features of the human body contain imperfections or awkward designs, such as the blind spot in the optic nerve, that "argue against an omnipotent creator and for a mindless, blundering, tinkering process that is not so much masterful as make-do."

The basic premise of the Barashes' book, that human beings are "perfectly good mammals, to be understood by looking in that mirror called science" will doubtless anger people of traditional religious or cultural beliefs. This is particularly unfortunate because it would be very difficult to find a more humane and enlightened book than Mammal in the Mirror. The authors quote extensively from the masterpieces of literature and philosophy to reinforce their contention that our connectedness to nature is an opportunity for humanity to grow in self-awareness.

Mammal in the Mirror is a model of popular-science writing. It can be read with advantage by a general reader unacquainted with the mitochondria, which are hard at work helping him to live and breathe, or by a person well versed in biology, who would like to share the company of two scholars who are passionate about life. The only real criterion for reading this wonderful book is a willingness to heed Immanuel Kant's motto, which the authors quote in their introduction: "Sapare Aude" - Dare to Know.