THE ANCESTOR'S TALE

A Pilgrimage to the Dawn of Evolution

By Richard Dawkins. Houghton Mifflin. 673 pp. $28

It's easy to imagine that the entire history of the universe is a kind of buildup to the appearance of Homo sapiens -- that the whole thing, somehow, is about us. Most writers on the subject of evolution (and I include a heartfelt mea culpa here) simply make a ritual genuflection to point out that the life history of humans is of no more fundamental importance than that of butterflies or Furbish's lousewort and then go on to talk only about humans. After all, it's humans who will be reading our books.

Richard Dawkins of Oxford University is a well known figure in evolutionary theory. His book The Selfish Gene set the tone for a decade of debate about the inclusion of the new science of genetics into our view of the past history of life -- an inclusion that is now a routine part of the field. In this book, he undertakes a sweeping overview of that history, but an overview emphasizing that the life story of every species is equally interesting.

Modeling his book self-consciously after Canterbury Tales, he imagines all species on Earth simultaneously beginning a journey backward in time, each following its own lifeline in a kind of pilgrimage to origins. As each species travels backward, it encounters others at points that Dawkins calls "rendezvous." At a rendezvous, we find the last common ancestor of the two species that are meeting. For example, by Dawkins's reckoning, human beings make their first real rendezvous between 5 and 7 million years in the past, with a primate whose lines of descent include us and the chimpanzees. At each rendezvous, there is a discussion of the fellow pilgrims we meet, then a "Tale," a la Chaucer. Thus, for example, as we trace human ancestry back, we have the Chimpanzee's Tale, the Beaver's Tale, as well as the Cauliflower's Tale (my personal favorite) and so on, right back to what he calls Taq's Tale, the story of an obscure bacterium (Thermus acquaticus) and a discussion of the origin of life itself. Each "Tale" goes into as much detail as is necessary to elucidate the scientific point illustrated by the rendezvous. The Cauliflower's Tale, for example, deals with the relation between rate of metabolism and body size, which seems to follow a regular trend for organisms from bacteria to whales.

This is great stuff -- intriguingly written, honest about the controversies that exist, clear about the science. Dawkins does not dodge complexity where it is called for but keeps it to a minimum and winds up giving us as full and clear a picture of the way life developed on our planet as you are likely to find anywhere.

In the end, I had only two general problems with this book, one technical, one stylistic. Dawkins is clearly what I have come to think of as a "gene guy" -- someone who wants to look at life from the perspective of DNA. Because of this, my sense is that he underplays the importance of fossils in his discussions. He claims, for example, that we could reconstruct the history of life just from living DNA, without any fossils at all. I am very skeptical of this claim, although this is a subject on which reasonable people can (and do) differ. It is never explicitly stated, but the book has a tone of genetic determinism, the notion that if you know an organism's DNA, you know everything important about that organism. There is virtually no mention of the importance of what are called epigenetic effects -- effects outside DNA that influence how an organism functions. I fear that coming to an understanding of how living things work isn't going to be as simple as sequencing a genome.

The stylistic problem involves Dawkins's disconcerting habit of occasionally dropping in snide asides designed to demonstrate, I suppose, his impeccable politically correct sentiments. For example, in talking about the development of agriculture in the Middle East 10,000 years ago, he takes a swipe at the American Army for not preventing the looting of the Baghdad museum. (He conveniently ignores the fact that most of what was missing wasn't looted but removed for safekeeping, and what looting took place was almost certainly done by museum employees, possibly before the war even started.) At first these little asides were merely irritating, but after a while they got really annoying -- kind of like being trapped at a cocktail party by the most pompous, supercilious member of the English department.

Dawkins is certainly entitled to hold and express his views, but they seem jarringly out of place in this book. He is far too good a writer, and too important a figure in the battle against scientific illiteracy, to allow these kinds of sophomoric self-indulgences to detract from a splendid piece of writing. *

James Trefil is Clarence J. Robinson Professor of Physics at George Mason University. His latest book is "Human Nature: A Blueprint for Managing the Earth -- By People, For People."

Mammal-like reptiles before the arrival of the dinosaurs