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Ape and Essence

GENOME The Autobiography of a Species in 23 Chapters By Matt Ridley; HarperCollins: 346 pp., $26

March 05, 2000|DANIEL J. KEVLES | Daniel J. Kevles is the author, most recently, of "The Baltimore Case." He is a professor at Caltech

Matt Ridley's book is, as he puts it, "a whistle-stop tour of some of the more interesting sites in the genome and what they tell us about ourselves." A British science journalist, Ridley is a lucid, engaging and enthusiastic guide to the double-helical DNA that comprises our inheritable human essence. He is the author of two previous books--"The Origins of Virtue" and "The Red Queen"--that deal with evolution, particularly the evolution of human nature and cooperation. "Genome" also attends to the history of our species as some scientists have found it revealed in our genes--the autobiographical reference of Ridley's subtitle, its meaning enriched by commentaries extracted from comparison with the genes of other species.

In the main, however, Ridley leads us on a journey through the biology of human characteristics, focusing on data that bear--or at least are claimed to bear--on the genetics of physical, behavioral and mental traits. The data have come from a number of fields, including neuroscience, brain studies and research into the dynamics of the cell, but each has been increasingly informed by the dizzying acceleration in the acquisition and computer analysis of genetic information, not only about our own species but also about, notably, fruit flies, worms and mice.

Ridley, whose enthusiasm for genetics at times gets the better of him, asserts that "in just a few short years we will have moved from knowing almost nothing about our genes to knowing everything." The fact of the matter is that, though scientists will shortly identify the sequence of chemicals that compose our genome and encode our humanness, it will be a long time before the functions of all our genes--we have perhaps 100,000--are understood. Nevertheless, we are learning much about ourselves from research on the genes of other species because a number of their genes are similar to ours in composition and function. The cracking of the genetic code sealed with chemical certainty our Darwinian affinity with the great apes. It also confirmed post-Darwin expectations that, as Ridley puts it, "all life is one; seaweed is your distant cousin and anthrax one of your advanced relatives."

"Genome's" 23 chapters nominally deal, one each, with our 22 non-sex chromosomes and with the sex chromosomes (X and Y). Pretty much ignoring the chromosomes in practice, Ridley takes one of the genes on each as a starting point to explore a trait to which it is putatively relevant. The real subjects of his chapters are characteristics such as intelligence, learning, instinct, self-interest, self-assembly (i.e., organismic development), disease, cures, personality, sex and memory.

Research in many of these areas has yielded fascinating results--for example, the discovery of "homeoboxes," clusters of genes, many of them similar across species, that control the development of the fertilized egg into a multicellular, fully formed organism. "At the level of embryology we are glorified flies," Ridley writes. At other levels, too: Studies with fruit flies have revealed genes that figure in memory and aging. Cancer has been exposed through studies of viruses, chicken cells and mice as a disease of genes gone wrong or made to go wrong by insults such as tobacco tar. One class of genes has been found--with implications for chemotherapeutics--to encourage misbehaving cells to commit suicide. DNA testing of seemingly monogamous birds has revealed that the female conceives children with males that are not her mate, a finding echoed in genetic testing for paternity among human beings.

Although such results are for the most part rock-solid--work in the genetics of development has won a Nobel Prize--some of the claims that Ridley reports in the genetics of behavior and psychology are questionable, to say the least. They include, for example, the detection of a linkage between male homosexuality and a stretch of DNA on the X chromosome; the correlation of super-brightness in a group of children with a sliver of DNA on chromosome 6; and the report that people with two long copies of a certain gene are distinctly more "novelty seeking" than people with two short copies of the gene. Ridley contends that a gene somewhere on the X chromosome "enhances the development of social adjustment"--for example, the ability to understand other people's feelings--and he writes summarily that "the brain is an organ with innate gender."

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