Natural Selection What To Read On The Way To The Boneyard. By Gregory McNamee Song of the Dodo, by David Quammen (Scribner). Hardcover, $32.50. ONETIME TUCSONAN David Quammen has given us several books with The Song of the Dodo, which weighs in at more than 700 pages--all of them uncommonly well written and admirably instructive. At the first and simplest level, Quammen delivers a book of literary travel, taking the reader to exotic locales like Bali, Mauritius, Iceland, Galapagos, Madagascar. At another, he offers a finely detailed journalistic account of how ecological science is done, how close fieldwork combines with theoretical reflection to advance our understanding of the natural world. At another, he charts the grim course of extinctions on this chewed-up planet. At still another, Quammen presents an accessible explanation of Robert MacArthur and E.O. Wilson's highly influential theory of island biogeography, which has revolutionized population biology since its publication in 1967. And Quammen manages, against the odds, to merge these discussions--and much more--into a single, coherent narrative. Islands are, by tautological definition, geographically isolated: bits of land, large or small, separated from other bits of land by water. That isolation, Quammen remarks, quoting the biologist Ernst Mayr, is "the flywheel of evolution": On islands, animal and plant species separate and transform more markedly than elsewhere. Among MacArthur and Wilson's contributions was the metaphorical extension of this commonplace to island-like areas: mountain tops, say, or more pointedly, parks and wilderness areas surrounded by developed landscapes. The more space available, the greater the number of species that will develop, an insight that has been of critical importance lately in the debate over designating federally protected wilderness in the continental United States and elsewhere, now a checkerboard of the wild and the paved or plowed. Small islands lose more species by extinction than do large ones, Quammen observes at several points in his book, and if we wish life to thrive in all its diversity, then we will have to make large islands in the land where no islands, or small ones, now exist. This is an obvious enough observation, but one that may find little room in an economy driven by notions of growth, in a world where the population of Homo sapiens is expanding by frightening logarithmic leaps. Along the way, Quammen gives us thumbnail biographies of important figures like Charles Darwin and the often overlooked naturalist Alfred Wallace, whose 1857 paper "On the Natural History of the Aru Islands"--now "interred, like a Gnostic gospel, in a cave of oblivion"--set biological theory on a new course. Wallace's contributions were obscured, Quammen writes, partly thanks to Darwin's own machinations, which the author does not hesitate to suggest were "scummy behavior." You will learn, reading Quammen's book, that Komodo dragons evolved to feed on a diet of elephants; that, in a wonderfully clear discussion of genetic theory, "a gene is a rubric that can be embodied in various ways"; that the slightest tinkering with the chain of being can cause the disappearance of a species; and that the call of Raphus cucullatus, the dodo, extinct since 1690, "is forever unknowable because no human from whom we have testimony ever took the trouble to sit in the Mauritian forest and listen"--an object lesson of universal application, and one that ought to be introduced into the discussion the next time Congressional radicals try to dismember the Endangered Species Act. You will also learn, depressingly enough, that "the current cataclysm of extinctions is...likely to stand among the worst half-dozen such events in the history of life on Earth." Allowing that it is possible to change this course, but unlikely, Quammen invites us to take comfort in the fact that we humans will almost certainly be among the species we escort to evolution's boneyard, and that the Earth will survive and recover--in, say, 20 or 30 million years.

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