Life: A Natural History of the First Four Billion Years of Life on Earth by Richard Fortey, Alfred A. Knopf, $30, 346 pages.




The News & Observer


July 5, 1998

Evolution of opinion

At any given time, a scientific discipline is usually dominated by one or two individuals. Newton, Einstein and Feynman were the pre-eminent physicists of their day. Darwin and Huxley played the same role in 19th-century biology, and Linus Pauling was the man in chemistry for much of this century. These people are mental giants, and they don't suffer fools gladly; crossing intellectual swords with them is as dangerous as crossing real swords with the three musketeers. Consequently, it is refreshing to read a book that challenges one of today's icons.

The man challenged is the polymath and Harvard professor Stephen J. Gould. The author, Richard Fortey, a paleontologist at the Natural History Museum of London and a Fellow of the Royal Society, is aware of Gould's status. "If paleontology has a priesthood," he writes, "Steve Gould is the pontiff." Nevertheless, Fortey takes him on.

"Life" isn't about Gould, of course; he plays only a small but important role in the book. It is rather a biography of life on this planet. Fortey traces the evolution of living organisms through 4 billion years, from the earliest single-celled bacterium to the rise of dinosaurs to the small mammals that replaced them to man.

The scope of the book is immense and sometimes confusing. Fortey routinely dates the great events of life by referring to the geologic periods in which families of animals flourished or went extinct. As most of us don't have the dates of the Jurassic or the Permian periods firmly fixed in our minds, a geologic timetable would have been useful - I finally dug out a reference book to keep me on track. A few maps showing how the continents have moved over time also would have been helpful. These shortcomings aside, the book is easy to read. And as it follows the development of life on Earth, it takes the reader into the heart of the evolutionary process.

Under normal conditions, every organism produces more offspring than the environment can support. These offspring vary because of random mutations and the genetic variability inherent in sexual reproduction, and the survivors, of course, are the ones who pass on their genes. This process of natural selection produces organisms that change (or evolve) over time. And it leads to the central question of evolution: Do random variations in individuals, when honed by natural selection, result in a process that has a direction? Does the trend from bacteria to humans represent something we can call progress?

The answers paleontology provides depends on the paleontologist asked. When early 20th century researchers discovered the Burgess Shale - a site in British Columbia that contained numerous well-preserved fossils laid down 570 million years ago, during the early Cambrian Period - they noticed how strange the fossils were but still placed them in the "progressive" view of evolution.

But in 1989, Gould weighed in with a contrary opinion in his best seller, "Wonderful Life." Focusing on the fossils' distinctiveness, he argued that many could not be linked to subsequent species. Yet, he noted that the species that survived to populate the world and those that did not seemed equally "fit." If a different handful had survived, later life forms would have looked much different. The Earth's occupants, he wrote later, "do not form an evolutionary sequence, but rather a motley series of disparate forms." Evolution, he concluded, is directionless, a simple matter of chance, dependent more on luck than genes.

Fortey is appropriately cautious in challenging Gould. "The Burgess Shale," he writes, "however, was one case where he [Gould] has, I think, been fallible." Pointing to studies conducted after Gould's book, he notes that "many Cambrian animals actually do make sense in light of what came after them and of what is still alive today." But his differences with Gould also are philosophical. For example, Gould admits that there is a trend toward more complex organisms, but he argues that this is merely an artifact of life's simple bacterial origins. The only way life could evolve, Gould maintains, is toward greater complexity, so don't mistake that trend for progress. Furthermore, bacteria are still around, and their longevity makes them at least as successful as oak trees or blue whales - or humans.

Looking at the same evidence, Fortey writes, "It is almost impossible to describe ... [evolution] without using the language of 'improvement.' " In other words, perhaps there is a direction to evolution, toward more adaptable and better designs. And if such a trend exists, one might call it "progress."

Even Charles Darwin was ambivalent about the issue. He understood that natural selection produces only local adaptations. Thus, organisms adapted to heat might be replaced by new cold-tolerant species when the climate cools. And who can say that the surviving species represents "progress"? Yet near the end of "Origin of Species," he wrote: "As natural selection works solely by and for the good of each being, all corporeal and mental endowments will tend to progress toward perfection."

In the end, Fortey also is ambivalent about the direction - if any - of evolution. He is willing to challenge Gould - but not to contradict him. He summarizes his views in the last chapter: "The greater story of life on our planet is partly a story of luck, of changes imposed upon the world by earthly and universal forces, and partly a story of genes, and finally a product of the changes life itself has wrought to modify the odds."

Does evolution have a direction? Has life progressed from lower to higher organisms, from poorer to better designs? Gould's arguments are compelling, and "Life" offers no definitive rebuttals. However, the book will educate you about how life evolved on Earth and might help you form your own opinion. I know it solidified mine; I have long suspected that evolution has a direction, that it favors complex organisms, which are more adaptable and therefore more successful. Paramecia evolved into elephants, but as far as we know, the reverse process has never taken place. Complexity isn't just a byproduct of life's humble beginnings; it is a real trend encouraged by evolution.

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