American Scientist

THE GREATEST SHOW ON EARTH: The Evidence for Evolution. Richard Dawkins. x + 470 pp. Free Press, 2009. $30.

We scientists are, by nature, an optimistic lot. Our profession demands optimism: We investigate complex phenomena, armed with little more than the scientific method—and with the conviction that reason, logic, empiricism and sweat will eventually prevail. And yet our optimism is not always rewarded. For here we are, 150 years after the publication of Charles Darwin’s On the Origin of Species, still trying to convey the not-so-new-information that evolution is the force that shapes the living world.

This past year has seen the publication of several excellent books for a general audience, some of them prompted by the celebrations surrounding Darwin’s 200th birthday. Richard Dawkins, who has already done much to make evolution accessible to the interested public, has contributed The Greatest Show on Earth, a book that will certainly burnish his reputation as one of the foremost presenters of science. It is the work of an optimist. Like others before him, Dawkins remains committed to the power of reason and animated by the belief that if only the right metaphor is brought to bear, the right simile used to illuminate the process, surely the “history-deniers” (his provocative term for modern creationists) will see the error of their ways.

Yet there are days when I think we evolutionary biologists might be missing the point. We cling to the idea that the denial of evolution and the rejection of material explanations for material phenomena must surely be the result of some misunderstanding that we can straighten out with clear examples and steadfast logic. Dawkins lays out the magnitude of such a task in a nine-page appendix. There he notes that a 2008 Gallup poll showed that 44 percent of Americans sampled believe humans were created by God within the past 10,000 years. Also, a survey conducted by Eurobarometer in 2005 showed that in Turkey, 51 percent of respondents rejected as false the proposition that “human beings, as we know them today, developed from earlier species of animals.” Although in Iceland, Denmark, Sweden, France and Britain only 13 percent or less said it was false, in Switzerland, Austria and Croatia 28 percent did. And in Turkey 42 percent accepted as true the proposition that “the earliest humans lived at the same time as dinosaurs.” Surely close to 100 percent of these same respondents would want their doctors to treat their bacterial infections with antibiotics that retain their effectiveness, not with agents to which bacteria have evolved resistance. The aphorism that there are no atheists in foxholes has a parallel here: Creationists check their hats at the clinic door.

Will well-crafted books about evolution such as this one change many minds? Probably not. At its worst, resistance to evolution and to its presence in the classroom is one more item in a cynical political agenda. Lobbyists and hucksters have distorted evolutionary biology and its implications as part of a broader effort to turn the clock back to some imaginary golden world in which humans held a privileged place in all of creation, and all of creation was theirs to subdue. Of late, to serve a narrow political agenda, this camp has bundled together the denial of evolution with the denial of global warming. No book is likely to make an impression on these demagogues.

But I’m convinced that many who reject evolution do so not out of cynicism, but out of fear: fear of the unknown, fear of a world that is random, fear of a universe not centered on us. These fears are nothing new. In 1669, the French philosopher Blaise Pascal admitted that “the eternal silence of infinite spaces fills me with dread.” He was articulating a common response to the profound scientific revelation of his time: The Earth is not the center of the universe. Renaissance humanism had granted human beings fundamental dignity; nevertheless, the discovery that we were not at the center of things was unsettling.

Can The Greatest Show on Earth allay the fears that create some fraction of the “history-deniers”? Perhaps. But as Dawkins himself makes clear, in an entertaining but depressing transcript of an exchange he had with an antievolutionist he interviewed for a television documentary, there may be no book, no argument, no weight of evidence that will move some people from their rehearsed positions. This book is addressed to the small sliver of the undecided and to those who will enjoy a book that brings the modern evidence for evolution together in a single accessible volume.

The Greatest Show on Earth treats us to a graceful discussion of the meanings and measures of time in evolution, from radiometric dating to the stately pace of molecular change. Dawkins makes it clear that a rejection of evolution implies a rejection of the most fundamental physical constants and forces of the universe. In so doing, he embeds evolutionary logic where it belongs, at the core of any rational understanding of the physical world.

In two accessible chapters that debunk the frequent creationist claim that there are no “intermediate forms” in the fossil record, he chronicles just how much the past two decades of paleontological finds have fleshed out the catalogue of such forms. He is similarly compelling when he discusses the creative power of selection to shape biological form and function. Imitating Darwin’s rhetorical strategy in The Origin, Dawkins moves seamlessly from the power of artificial selection to shape crops and livestock to the power of natural selection to shape flowers and the tongues of pollinators. This section includes a few well-known examples (pigeons and chickens) and also introduces some newer, fascinating stories. Thus we come to know about the unexpected consequences of selecting silver foxes for easier handling—doglike physical and behavioral traits emerge. Using examples from the bacterial, plant and vertebrate worlds, from laboratory experiments and natural ecological accidents, Dawkins captures some of the excitement of contemporary evolutionary biology and makes it clear that we have come a long way since 1859.

At its best, The Greatest Show does much more than simply lay out the objects—fossil and living, molecular and ecological—that constitute the evidence for evolution. In prose that is both engaging and approachable, Dawkins emphasizes some of the mechanisms that drive the evolutionary process, such as mutation, selection and gene transfer. This emphasis on evolutionary process is important for two reasons. First, it underscores the rules that make evolutionary biology a powerful and predictive science, not just a collection of anecdotes about adaptations. Perhaps more subtly, the emphasis on process highlights the ongoing nature of evolution, making it clear that contemporary organisms are not the end products—let alone the goals—of evolution.

The book repeatedly returns to a set of important ideas that reveal how simple material forces can give rise to complex outcomes, underscoring the fact that design need not imply a designer. Maybe most convincing in this regard is Dawkins’s discussion of the many simulations that have proved useful in understanding the evolutionary process. From simple computer programs that mimic the geometry of shell formation or the branching architecture of plants, to more complex simulations that model the diffusion of molecules important to development, the message is the same: From simple rules, complicated organisms grow. Similarly, Dawkins emphasizes that many seemingly complicated outcomes can result from the interaction of large numbers of entities—ants, birds or cells—each endowed by evolution with a simple and experimentally accessible set of rules governing its behavior. No need to invoke designers, intelligent or otherwise, when time and an enormous number of simultaneous ongoing evolutionary experiments will suffice.

To be sure, The Greatest Show on Earth sometimes suffers from Dawkins’s extreme positions on certain issues. A self-described hyperadaptationist, he remains convinced that natural selection can craft organisms as needed to ensure that they will fit their environments. In those rare cases in which organisms appear to fall short of being perfect machines, Dawkins invokes trade-offs and compromises due to conflicting selective demands; in keeping with his conviction that organisms are simply DNA’s way of making more DNA, he never doubts that selection rules alone. Not everyone agrees. The more nuanced view within evolutionary biology is that a complex interplay occurs between the power of selection and the constraints of the organism. Organisms are not like clay. They have a previous history, a coherent genome, and a narrow developmental pathway that they must travel from conception to adulthood, all of which temper, transform and on occasion hinder the action of selection.

Ultimately, The Greatest Show on Earth reminds the reader of the power of a single idea: that the appearance and behavior of living creatures, their distribution, their history and their imperfections are all the consequences of descent with modification. Evolution is a powerful concept, but it is not necessarily a comforting one. At the beginning of the 21st century, in a world that we acknowledge as increasingly complex, we still crave reassuring and simple explanations. But it is not the job of scientists to supply simplicity or reassurance. Our job is to be thorough and accurate, and in a complex world, that usually means offering complex and often incomplete explanations. In the end, our obligation is to witness and chronicle the greatest show on Earth, even as we acknowledge that we are only bit players in it.

Robert L. Dorit is an associate professor in the Department of Biological Sciences at Smith College.