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Design for Living

By Susan Okie

Sunday, February 13, 2000; Page X03

GENOME

The Autobiography of a Species

In 23 Chapters

By Matt Ridley

HarperCollins. 344 pp. $26

Reviewed by Susan Okie

By 2002, an international team of scientists is expected to piece together a readout of the complete recipe for a person. Three billion letters long, the instructions would fill a stack of books 150 feet high. Even when we have it in hand, we won't know how to cook with it -- and it will take decades to figure out what it all means. So why are researchers already so confident that decoding the genome will be a scientific watershed, a Rosetta Stone likely to teach us what makes us human?

Matt Ridley's marvelous new book goes a long way toward answering that question. Upon an ingeniously simple framework -- one chapter for each of the 23 pairs of human chromosomes -- Ridley has built a sweepingly ambitious work that tackles, in lucid and often poetic prose, many of the biggest questions in biology and beyond: How did life begin? What distinguishes us from chimps? What determines how smart we are? Why are men and women so often at odds? Why are some people shy and others adventurous? Why do we grow old and die? And (perhaps the central question) if genes guide our character and behavior, is there such a thing as free will?

Despite the book's structure, chapters often have only the most tenuous connection with individual chromosomes. Instead, under broad themes such as "conflict," "sex" and "immortality," Ridley sketches the history of modern genetics and details the hottest discoveries and the most engrossing controversies in the field. Consider the war between the sexes, which some researchers suggest is quite literally a battle of the genes. According to this theory, the large and influential X chromosome (the "female" sex chromosome that exists in two copies in women) has evolved genetic strategies for attacking the "male" Y chromosome, because traits that benefit the males of a species are often disadvantageous for females. In response, the Y has shed or shut down many of its genes as a means of self-protection, becoming a sort of stealth chromosome -- the smallest of the human 46 -- with just one powerful gene called SRY that contains everything needed to make an embryo male. As weird as this argument sounds, Ridley describes evidence that the battle is being played out in various species. In the butterfly Acrea encedon, for example, males are so biologically beleaguered that the sex ratio is 97 percent female.

A recurring theme in Genome is the misleading distinction between "nature" and "nurture," which Ridley argues is an overworked dichotomy that ignores the intricate interplay of genes and environment. Social scientists, he writes, have often unfairly equated heredity with implacable fate while portraying the environment as a friendlier, more mutable force molding human health and character. But genes don't operate in a vacuum: They can both respond to external influences and act to alter an organism's milieu. Furthermore, "genes are not there to cause diseases," and the ones that do predispose to illnesses (such as asthma or sickle cell anemia) have survived in our bodies for a reason -- often, because they protect against life-threatening infections that decimated human populations in the past. In a few cases, a single fatal genetic mutation -- like the one that causes the progressive dementia of Huntington's disease -- can write "a prophecy of terrifying, cruel and inflexible truth." But for most core human attributes like personality and intelligence, so many genes contribute that it's senseless to view ourselves as prisoners of genetic destiny. "The more we delve into the genome, the less fatalistic it will seem," writes Ridley. "The genome is as complicated and indeterminate as ordinary life, because it is ordinary life."

Ridley doesn't examine in detail the ethical aspects of new genetic advances and their implications for future social policy, although his discussions of the history of genetics, including the eugenics movement and the debate over I.Q. testing, are thorough and illuminating. On issues such as genetic testing and gene therapy, he comes down in favor of giving individuals -- but not institutions, government or society -- the choice of whether to seek and make use of personal genetic information. Even when a genetic test might reveal a depressingly high likelihood of developing a disease such as Alzheimer's, Ridley generally favors making such tests available to people who feel they would rather know than not know. (Such a test, called the APOE4 test, actually can help predict future risk of Alzheimer's disease.) Although there may be no way to fix a potentially dangerous mutation, Ridley argues, carriers of such mutations may use their knowledge to make decisions about lifestyle or childbearing or to try an experimental treatment.

A former editor of the Economist, Ridley is a superb writer whose exquisite, often moving descriptions of life's designs remind me of the best work of the late Lewis Thomas. Scorning hackneyed, imprecise metaphors (a gene, he insists, is nothing like a blueprint), he crafts some of the clearest explanations of complex biological processes that I have encountered. What's more, he captures their slippery beauty. Listen to his description of how life evolved:

"In the beginning was the word. The word proselytised the sea with its message, copying itself unceasingly and forever. The word discovered how to rearrange chemicals so as to capture little eddies in the stream of entropy and make them live. . . . The word eventually blossomed and became sufficiently ingenious to build a porridgy contraption called a human being that could discover and be aware of the word itself."

Susan Okie, a reporter on the national staff of The Washington Post, covers health and medicine.

© Copyright 2000 The Washington Post Company

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