Putting Theory to the Test
WHAT DARWIN GOT WRONG.
By Jerry Fodor and Massimo Piattelli-Palmarini.
Farrar, Straus & Giroux. 264 pp. $26
Americans love conspiracy theories. Many still think that shadowy plotters continue to cover up the identity of JFK’s “real” killers, and the popular notion that climate change is a hoax perpetrated by a cabal of self-interested scientists is now enjoying its second or third wind. The longest-running conspiracy theory in science, however, depicts a fiendishly complex effort by scientists over the past 150 years to prop up a bankrupt Darwinian theory in spite of what its critics see as massive and self-evident flaws. Although nothing in What Darwin Got Wrong suggests that the authors, Rutgers University philosophy professor Jerry Fodor and cognitive scientist Massimo Piattelli-Palmarini, believe that a conspiracy is afoot, their writing follows the usual pattern.
First, the authors set up a straw man. In this case, they do that by saying at the outset that the Darwinian theory of evolution involves two distinct parts: the concept of common descent, which holds that all plants and animals evolved from a common ancestor, and the theory of natural selection, which posits that random, inborn mutations in individuals selected by a survival-of-the-fittest process drive evolution forward. The authors stress that they reject only the latter theory, while erroneously contending that, historically, religious opponents have attacked only common descent.
Fodor and Piattelli-Palmarini’s central thesis is that random, inborn mutations chosen by a survival-of-the-fittest mechanism cannot generate the observed diversity of species in the time that has elapsed since life began on Earth. They point to the many non-random influences on variation (such as gene regulatory networks, which control cellular processes, and horizontal gene transfer, in which an organism incorporates genetic material from another organism without being a descendant of that organism) debated among biologists today, and, somewhat separately, assert that natural selection logically cannot work. Their philosophical assault on natural selection has two parts. They argue that biologists simply err in speaking about selection without providing for a human, divine, or natural-law selector. Further, they throw in their version of the shopworn philosophical argument that natural selection is a meaningless tautology: Of course, if fitness is equated with survival, only the fittest will survive. (In this sense, the Newtonian equation F = ma is a tautology too, yet physicists still find it useful.) Though the authors present their critique as new, it is similar to countless assaults on the theory of natural selection over the past century and a half. What this book adds is a useful survey of newer examples of non-randomness in evolution.
Contrary to their claim that common descent is the bugbear of those who dispute evolution, the historical controversy, especially in religion, focused on the idea of natural selection, which undermined natural theology by depicting the origination of species as a ruthless, random process, apparently inconsistent with the character of a loving Creator, rather than on the concept of common descent, which can posit God as the designer of benign evolutionary law. After all, as the illustrious late-19th-century American cleric Henry Ward Beecher said, “Design by wholesale is grander than design by retail.” It is the theory of natural selection that still riles the intelligent design movement, many of whose leaders (such as Lehigh University biochemist Michael Behe) accept common descent.
Even more bewildering is the authors’ contention that Charles Darwin conflated common descent and natural selection into a single idea. Darwin clearly differentiated between the two parts of his theory, and recognized that the concept of common descent stood on a much firmer foundation. In 1863, he wrote to Harvard botanist Asa Gray, “I care much about Natural Selection; but that seems to me utterly unimportant compared to the question of creation or modification.” Eleven years later, when the conservative Princeton theologian Charles Hodge launched the American culture wars over evolution with his book What Is Darwinism? it was natural selection—not common descent—that led him to equate Darwinism with atheism. Analogous reasoning drove William Jennings Bryan to ignite the populist crusade against teaching evolution that culminated in the 1925 Scopes trial. Bryan had made his peace with common descent, at least for everything except humans; it was the use of a survival-of-the-fittest mechanism to explain human nature that enraged him.
The scientific community has never monolithically regarded natural selection as the sole mechanism of evolution. Certainly Darwin did not. He freely worked sexual selection, which involves the preference of certain characteristics by mates, and group selection, which propagates social qualities that help groups survive, into his account of evolution—particularly for the development of behavioral traits. Further, he recognized that selection alone could not cause evolution; selection would have to operate on phenotypic variation within species. Although Darwin initially believed that minute, random, inborn changes could supply much of the variation needed for selectionism to operate, even he retreated from this view. With the development of his theory of pangenesis in 1868, Darwin increasingly turned to the inheritance of acquired characteristics to supply the variation needed for evolution, which inevitably diminished the role of natural selection.
Throughout the late 19th century and into the early 20th century, biologists hotly debated how evolution operated, much as they still do today. Leading evolutionists were particularly divided over the cause of variation within species and the sufficiency of natural selection to drive the evolutionary process, the main concerns raised by Fodor and Piattelli-Palmarini. A survey of early-20th-century evolutionists would find significant support for at least four different theories of organic variation: Lamarckism, which relies on the heritability of acquired characteristics; orthogenesis, which posits internal developmental forces within living things; gross mutation, in which new species are created in a single leap without an incremental process of natural selection; and hybrid crossing, in which existing gene-based traits flow from one species to another.
All of these theories relegate natural selection to a less fundamental role in evolution than it would have under a theory that relies on randomly generated minor variants of phenotypic traits to explain the appearance of new forms of life. By 1900, there was no scientific consensus beyond the essential fact of common descent. The sort of “Darwinian” thinking depicted in this book as hegemonic was actually in full retreat. Stanford University entomologist Vernon Kellogg captured the general sentiment when he wrote in 1907, “While many reputable biologists today strongly doubt the commonly reputed effectiveness of the Darwinian selection factors to explain descent, . . . the descent of species is looked upon by biologists to be as proved as part of their science as gravitation is in the science of physics.” The doubts cited by Fodor and Piattelli-Palmarini as revolutionary today were widely held a century ago—and never disappeared.
In the mid-20th century, following the integration of classical genetics into evolutionary biology, a consensus emerged that, at least in large part, the gene pool held a sufficient reservoir of variation to fuel evolution through natural selection in response to isolation and environmental change. This so-called neo-Darwinian synthesis was selectionist, to be sure, but it did not exclusively rely on random genetic variation of the kind that this book decries as unable to fully account for evolution. Further, even as the consensus view hardened in the 1950s, many biologists continued to see hybridization as a critical source of variation, particularly in plants, and allowed for random genetic drift that evolved new species through the isolation of small groups rather than competition within large groups. In What Darwin Got Wrong, the authors concede that random genetic variation does cause evolution in some cases, a finding that is consistent with the neo-Darwinian synthesis.
In recent years, as this book illustrates, the consensus view of evolution has softened again, in response to research suggesting additional sources for phenotypic variation beyond minor genetic alterations and preexisting diversity in the gene pool. These alternatives range from horizontal gene transfers and hybridization to developmental forces (or “evo-devo”) and epigenetic modification. Even large-effect evolutionary mutations are back in vogue among some biologists. Such concepts may diminish or alter the role of natural selection, but they do not undermine the case for evolution. This book is at its best when summarizing these recent developments in evolutionary science. But the authors are wrong to suggest that they represent something fundamentally new in biology.
From Darwin on, biologists have discussed and debated how evolution operates. Science progresses by testing and improving old theories. Darwin continually adjusted his ideas during a lifetime of research. He was not dogmatic. First and foremost, like the authors of this book, he maintained the centrality of common descent to any rational understanding of life. Fodor and Piattelli-Palmarini assert that such recent developments as evo-devo somehow undermine the statement of legendary neo-Darwinist Theodosius Dobzhansky that “nothing in biology makes sense except in light of evolution.” So far as I know, all the researchers the authors cite would side with Dobzhansky by asserting that nothing in their work makes sense except in light of evolution.
By writing under the title What Darwin Got Wrong and claiming that as outsiders they can connect the dots to undermine the supposed Darwinist hegemony in biology, Fodor and Piattelli-Palmarini do the discipline a disservice. They begin their book by noting, when they describe their straw-man view of Darwinism, that biologists typically deny being “‘that’ kind of Darwinist.” But even Darwin was not “that” kind of Darwinist. Evolutionary biology is a robust and dynamic field that continues to enrich established theories through new research. If the theory of evolution were on the ropes, we’d hear about it first from ambitious biologists seeking to promote their research findings.
In their introduction the authors make a point of stating, “We both claim to be outright, card-carrying, signed-up, dyed-in-the-wool, no-holds-barred atheists.” After studying the history and development of evolutionary biology for a quarter-century, I’ve yet to understand why this matters. A large number of scientists, including many evolutionary biologists, are religious. Some critics of evolution are secularists. Scientific theories should be judged on their merits as testable, naturalistic explanations for physical phenomena rather than on theological or political grounds. It is called methodological naturalism, and Darwin (who never called himself an atheist) pioneered its use in biology.
The authors explicitly accept these ground rules for doing science and concede that Darwin followed them in his work. “It is our assumption that evolution is a mechanical process through and through,” they write. If it is, then by following Darwin’s approach of hypothesis and testing, science should arrive at an ever closer approximation of how evolution operates. That is what we are witnessing today. The authors could have better served their stated cause of pointing out the diversity within evolutionary science and the breakdown of the supposedly hyper-rigid neo-Darwinian synthesis by stressing how far biologists have come using Darwinian methods rather than by presenting recent developments as a sharp break from the past. But if they had followed that approach, they might not have attracted much attention for their book.