The Evolutionary Wars

On December 13 of last year The New Yorker published a startling essay by Robert Wright entitled "The Accidental Creationist" with the subtitle: "Why Stephen Jay Gould is bad for evolution."

Who is Robert Wright and who, if he needs any introduction, is Stephen Jay Gould? And why, in Wright’s opinion, is he "bad for evolution"?

Robert Wright is a science journalist and widely published author who fancies himself to be a "neo-Darwinian" evolution theorist. He is a contributing editor at The New Republic, Time Magazine, and Slate. He has also written for the Atlantic Monthly, the New Yorker, and the New York Times Magazine. He previously worked at The Sciences magazine, where his column "The Information Age" won the National Magazine Award for Essay and Criticism. So people do pay attention to his writings,

Stephen Jay Gould, Steve to his friends, on the other hand is a well known evolutionary scientist, with a long, distinguished…and controversial…career. Like Sagan, the general public knows him from his popularizations. Gould is respected, he is a member of the National Academy of Sciences (something Carl Sagan never achieved), and he is much loved. He writes a monthly column ("This view of life") for Natural History. Many of his essays have been collected and republished between hard covers.

Now, evolution is a fact, much contested by creationists and especially by their pseudo-scientific offspring, the creation scientists. Theories of evolution attempt to explain how it happens, the mechanisms that drive it. In recent decades, the tools offered by molecular biology have been extremely useful in this enterprise. But not all evolutionists agree on those mechanisms; they have their own favorite theories.

To be useful, a scientific theory must not only explain known phenomena, it must be able to predict hitherto unknown phenomena. These "predictions" need not necessarily concern future phenomena. A prediction can be simply where to look for something that had not been previously observed. Alternatively, it can show how different phenomena, previously unrelated, in fact are causally related.

An example of such a prediction is the recent discovery of wrist notches on early hominid bones stored in a Smithsonian warehouse that had never been observed before. A paleontologist went into the warehouse to look for these notches because knuckle walkers, the great apes, had these notches to lock their wrists when walking around on all fours. His conclusion, our ancestors were knuckle walkers.

Because the DNA of ancient fossils is generally inaccessible, Jurassic Park to the contrary notwithstanding, paleontologists mostly judge by morphology, the shapes of the fossils, the method used by Linnaeus to create his classification scheme.

Piecing together, then, how different life forms evolved over geologic time, the paleontologists find long stretches with gradual change of particular life forms. Then there’s a gap, and after the gap (going from the more ancient to the more recent), there’s a sudden radical change. Considering geologic time, the gap is "small," a few hundred thousand or a million or so years. Of course, there are life forms that persist relatively unchanged through all geologic time–the so-called "living fossils."

But the record also shows times of major change. One such time is known as "the Cambrian explosion," when the record in the rocks shows an enormous burst of new species appearing,

Considering such apparent discontinuities in the fossil record, Gould developed in 1972 (with Niles Eldredge). the theory of punctuated equilibria, a revision of Darwinian theory that proposed that the creation of new species through evolutionary change may occur not at slow, constant rates over millions of years but rather in rapid bursts over periods as short as thousands of years, which are then followed by long periods of stability during which organisms undergo little further change.

In the ensuing 30 years there has been a constant guerilla battle between the "neo-Darwinian" "gradualists," among them such other well-known evolutionists as Richard Dawkins and John Maynard Smith, on the one hand, and the punctuated equilibrium partisans, on the other. This is a serious scientific controversy that attempts to address significant theoretical questions, questions about how we are to interpret "the record in the rocks."

The paleontologists are doing their best to fill in gaps in that record. Recently, for example, we heard about a minuscule primate that scurried about the forests in what is now China, about 35 million years ago, fitting just into the middle of a 20 million year gap in the "record," a "missing link." This animal, less than an ounce, smaller than a mouse, may have been one of our ancestors!

So, punctuated equilibrium attempts to explain periods of rapid and rich speciation, the creation of new species. There are two modes for speciation in nature: anagenesis and cladogenesis.

In anagenesis changes occur within a lineage; in cladogenesis a lineage splits into two or more separate lines. Anagenetic evolution has, over the course of 2,000,000 years, doubled the size of the human cranium; in the lineage of the horse, it has reduced the number of toes from four to one.

Cladogenetic evolution has produced the extraordinary diversity of the living world, with its more than 2,000,000 species of animals, plants, fungi, and microorganisms. This has been more difficult to explain.

The most essential cladogenetic function is speciation, the process by which one species splits into two or more species. Because species are reproductively isolated from one another, they are independent evolutionary units; that is, evolutionary changes occurring in one species are not shared with other species. Over time, species become more and more divergent from one another as a consequence of anagenetic evolution. Descendant lineages of two related species that existed millions of years ago may now be classified into quite different taxonomic categories, such as different genera or even different families.

Dawkins describes a kind of "arms race," where opposing lineages coevolve through their opposition as one mechanism for anagenisis. Usually these are predator and prey, where fitness on the one hand is the ability to capture and eat the prey, and on the other hand, the ability to evade the predator. A favorite example is the bombardier beetle. This beetle emits a very noxious spray when attacked. Wright thinks that Gould neglects this arms race. He writes: "One might expect that, given enough time, beetle predators would up the ante, developing some clever way to neutralize the beetle's noxious spray. In fact, they have. Skunks and one species of mouse, the biologists James Gould (no relation) and William Keeton have written, ‘evolved specialized innate behavior patterns that cause the spray to be discharged harmlessly, and they can then eat the beetles.’"

An example closer to home is the selective pressure on pathogenic microbes caused by our efforts to extirpate them by antibiotics. They are evolving resistance at a tremendous rate. We don’t evolve fast enough biologically to become immune to them, but our weapons do evolve. We constantly develop new, more powerful antibiotics to counter the evolution of resistant strains of our pathogenetic enemies, such as tuberculosis.

Creationists claim that we have never directly observed cladogenesis, one species turning into another. We all know about mutation within genes, the accumulation of small changes that may render an individual biologically fitter than its parents. The accumulation of such changes over many generations may result in major changes, such as the evolution of homo erectus into homo sapiens. But what could have induced the cladogenesis that resulted in the descent of chimpanzees, gorillas, and humans from a common ancestor?

Aside from small changes within genes, molecular biologists now recognize other, more drastic changes. There may be gene duplications, leading to the possibility of a duplicated gene being free to take on new functions. There are transpositions and recombinations, where genes may end up on different chromosomes. Finally, there may be entire chromosome replications. We know many useful plants that have doubled chromosome sets.

Evolution depends on ﾒselective pressure.ﾓ This is the concept that changes that improve the adaptation of an organism to the environment tend to be conserved, maladaptive changes tend to be eliminatedﾉin future generations. Neutral changes are not subjected to selective pressure and may drift unchecked. This is what drives Dawkinsﾕs ﾒarms race.ﾓ What does molecular biology applied to the concept of adaptive pressure have to say? There are genes that have been conserved through almost all of evolution, genes that are found in the simplest organisms andﾐwith only small differencesﾐin the most evolved. They serve very fundamental life functions. Selective pressure will tend to eliminate almost all changes in such genes. Now imagine that such a gene is duplicated, through a genetic ﾒmistake.ﾓ

The duplicated gene may reinforce the function for which it was ﾒdesignedﾓ or it may be essentially neutral, free to drift. Eventually it may take on a new and useful function, i.e., an adaptive function; an act of creation has occurred.

All evolution theorists agree that such changes occur at random. It is selective pressure that determines which survive and which perish.

Most radical changes are lethal, or at least render an individual maladaptive. Human males with an extra X chromosome are relatively infertile. Indeed, closely related but distinct species are not cross fertile. They cannot interbreed. Or, if they do, to produce hybrid offspring, the offspring are infertile. Such is the case of the horse, the donkey, and the mule.

If the radical genetic changes are adaptive, that is, render an individual fitter, how does such a mutant find a mate and give rise to a new clade, a new species? This is at present an unsolved problem of evolution theory•ﾒGod of the gaps.ﾓ

There are many and bitter polemics amongst the evolution theorists. E.O. Wilson, who climbed aboard the sociobiology bandwagon many years ago, acts as if his colleague, Gould, down the hall at Harvard, doesnﾕt even exist.

And now Robert Wright comes charging into the fray. He quotes John Maynard Smith, another eminent evolutionist, as having written somewhere, "Gould occupies a rather curious position, particularly on his side of the Atlantic. Because of the excellence of his essays, he has come to be seen by nonbiologists as the preeminent evolutionary theorist. In contrast, the evolutionary biologists with whom I have discussed his work tend to see him as a man whose ideas are so confused as to be hardly worth bothering with, but as one who should not be publicly criticized because he is at least on our side against the creationists."

But Wright disagrees. Gould, the atheist, gives aid and comfort to creationists?

Gould essentially says that the random nature of genetic change is such that there is no inevitability about the appearance of any given species. He says, turn back the clock and start over and you will have something entirely different. There is no natural law for the appearance on the stage of evolution of the human actor, homo sapiens sapiens.

Aha, says Wright, I gotcha! You are playing into the hands of the creationists. By claiming that nature does not lead inevitably to the appearance of human beings, by saying that there is no evolutionary reason for human beings, you are essentially allowing the view that there must have been an act of creation for that to have happened. On the contrary, says Wright, there is a directive force in evolution from the simple to the complex. We, or something like us, had to happen. Recently Time Magazine had a special issue to celebrate the person of the 20^th century. In an article on communication through the ages, culminating in the information technology revolution, Wright feels it necessary to include this:

In the New Yorker article Wright had this to say:

Let me read that again: … the Darwinian account of our creation, once stripped of the misconceptions that Gould has covered it with, is not only compatible with a higher purpose but vaguely suggestive of one. Who is it who is giving comfort to the creationists? Wright goes on:

The fact is that biologists have discovered organisms that seem to have shed genetic material, have become simpler, to cope with special environments.

Wright has quoted Maynard Smith against Gould. He is not above misquoting Gould himself. He charges Gould with having declared the "death of Darwinism," Thereby causing creationists to rejoice. As Maynard Smith himself tells it, it was the Manchester Guardian that invented that story, "merely because [Gould] had pointed out some difficulties the theory still faces." Let us now dispose of Wright’s claim that Maynard Smith has a very low opinion of Gould. Maynard Smith’s book "Games, Sex and Evolution" is full of complimentary references to Gould. There are also respectful differences of opinion, but none of the put-down nature that Wright cites. He writes: "I hope it will be obvious that my wish to argue with Gould is a compliment, not a criticism."

What is Wright’s main gripe about Gould? Gould points out that evolution proceeds by trial and error, i.e., random changes and natural selection to eliminate or reinforce those changes. There is no inherent reason for humans to have evolved. Indeed, if we turn back the evolutionary clock and start over again, it is most likely that humans would not have evolved. This says Wright is what creationists seize on to say voilá, God must have made us. In fact, the creationists have used Gould’s writings to justify their views, much to Gould’s annoyance. And that is "why Stephen Jay Gould is bad for evolution." Gould denies "progress" in evolution.

But so does Maynard Smith. Already on page 4 of his book on "The Major Transitions in Evolution" he disposes of "progress" in the same terms that so annoy Wright in Gould.

Wright, the author, has a wonderful line describing this view in his attack on Gould: "Gould’s version of evolution–a stumbling, bumbling process that just happened to lead, Mr. Magoo-like, to Einstein, Mother Teresa, and the Internet." Yes, that is evolution and it’s wonderful. Science journalists should report the evolutionary war, not enter it!

It is so!

Copyright 2000, Morton Nadler; Commercial Duplication Prohibited

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