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You Say You Want an Evolution?

THE IMPACT OF THE GENE: From Mendel's Peas to Designer Babies, By Colin Tudge, Hill and Wang: 376 pp., $27; THE COOPERATIVE GENE: How Mendel's Demon Explains the Evolution of Complex Beings, By Mark Ridley, The Free Press: 324 pp., $26

January 06, 2002|ROBIN MARANTZ HENIG

The gene is hot stuff these days. Long before the first draft of the human genome was published last winter and thrust us into the Age of the Genome, the gene has been used to explain a whole raft of human facts of life: susceptibility to malaria or AIDS; traits like adventurousness and shyness; homosexuality; obesity; the inexplicable competing urges toward fidelity and straying.

Now come two books by two of the most highly regarded science writers in England, both eager to add their voices to the international paean to the double helix. (And this doesn't even count the recently published "Life Script" by Nicholas Wade or "Dinner at the New Gene Cafe" by Bill Lambrecht.) Each has taken a familiar biological argument and recast it, with differing degrees of success, entirely in terms of the gene.

In the first, Colin Tudge, author of such notable books as "The Variety of Life" and "The Second Creation," offers a concise history of the early days of genetics that culminates in a defense of the controversial field of evolutionary psychology (the newer, less-inflammatory term for "sociobiology," which caused an uproar when introduced by Harvard zoologist E.O. Wilson a generation ago and was immediately branded racist, reductionist and evocative of all the worst notions of eugenics and the quest for genetic purity). "The Impact of the Gene" thus becomes two books, one about the past and one about the present, with the gene providing explanatory power for a contemporary field that Tudge practically takes on faith.

In the second book, Mark Ridley (no relation to his countryman and fellow science writer Matt Ridley, author of the wildly popular "Genome"), a professor of zoology at Oxford, argues that the evolution of complex animals was by no means inevitable, is in fact counterintuitive and can best be understood in terms of the four-letter code of DNA. He borrows his title, "The Cooperative Gene," from the idea of a "selfish gene" first propounded by Richard Dawkins, who made the case that not only is a chicken merely an egg's way of making another egg (a phrase usually attributed to Samuel Butler), but that all of us, no matter how complex or talented or beloved, are merely DNA's way of making more DNA.

"If the business of life is to copy genes," Ridley writes, "most of our physiology suggests a loss of focus during evolution." By this he means not that Dawkins is wrong, but that the "selfish gene" idea is insufficient to explain how life evolved from simple, one-celled beings to the complex, highly organized living systems that walk on, swim under or fly above the Earth.

"The evolution of complex life required a mechanism of inheritance with an inherently random component," Ridley writes. "Somewhere between the bacteria and us--perhaps at about the stage of simple worms--God did have to start to play dice." So he creates a little mascot, "Mendel's demon," to help explain the rules of that celestial crapshoot. Calling it "Mendel's demon" is, of course, Ridley's nod to Gregor Mendel, the so-called father of genetics, because Mendel recognized that the units of heredity are randomly reshuffled every time a new generation is created.

The theorized behavior of "Mendel's demon," however, isn't demonic in the least. According to Ridley, it's "a law-enforcing kind of demon. It redirects the laws of biology to a more creative, rather than destructive, direction." In effect, it imposes order on a chaotic process, taking the form, ultimately, of increasing complexity.

Ridley focuses his argument about the evolution of complexity on a few crucial points: copying errors in the transcription of DNA and how they are passed on; natural selection and how it acts on offspring with genetic mistakes; and the evolution of sex. But despite Ridley's lighthearted touch, reading his book can be pretty tough going.

"The Impact of the Gene" is easier to read. The first half is a quick overview of the history of genetics, devoted primarily to retelling the little that's known about Mendel, a Moravian monk who spent seven years conducting research on inheritance patterns in pea plants, presented his results in a two-part lecture in 1865 and was promptly forgotten. Mendel died in 1884 thinking his conclusions about inheritance must have been wrong--but it turned out he was merely ahead of his time.

In 1900, his original paper was rediscovered, and scientists had amassed sufficient insight by this time to see it for what it was: a brilliant and clear demonstration of the existence of discrete units of heredity, which within a few years would be known as genes.

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