Note: This is Part 7 in a series reviewing Jerry Coyne’s Why Evolution Is True. Read Part 1 here, Part 2 here, Part 3 here, Part 4 here, Part 5 here, and Part 6 here.
Coyne writes that Darwin “had little direct evidence for selection acting in natural populations.” Actually, Darwin had no direct evidence for natural selection; the best he could do in The Origin of Species was “give one or two imaginary illustrations.” It wasn’t until a century later that Bernard Kettlewell provided what he called “Darwin’s missing evidence” for natural selection — a shift in the proportion of light- and dark-colored peppered moths that Kettlewell attributed to camouflage and bird predation.40
Since then, biologists have found lots of direct evidence for natural selection. Coyne describes some of it, including an increase in average beak depth of finches on the Galápagos Islands and a change in flowering time in wild mustard plants in Southern California — both due to drought. Like Darwin, Coyne also compares natural selection to the artificial selection used in plant and animal breeding.
But these examples of selection — natural as well as artificial — involve only minor changes within existing species. Breeders were familiar with such changes before 1859, which is why Darwin did not write a book titled How Existing Species Change Over Time; he wrote a book titled The Origin of Species by Means of Natural Selection. “Darwin called his great work On the Origin of Species,” wrote Harvard evolutionary biologist Ernst Mayr in 1982, “for he was fully conscious of the fact that the change from one species into another was the most fundamental problem of evolution.” Yet, Mayr had written earlier, “Darwin failed to solve the problem indicated by the title of his work.” In 1997, evolutionary biologist Keith Stewart Thomson wrote: “A matter of unfinished business for biologists is the identification of evolution’s smoking gun,” and “the smoking gun of evolution is speciation, not local adaptation and differentiation of populations.” Before Darwin, the consensus was that species can vary only within certain limits; indeed, centuries of artificial selection had seemingly demonstrated such limits experimentally. “Darwin had to show that the limits could be broken,” wrote Thomson, “so do we.”41
In 2004, Coyne and H. Allen Orr published a detailed book titled Speciation, in which they noted that biologists have not been able to agree on a definition of “species” because no single definition fits every case. For example, a definition applicable to living, sexually reproducing organisms might make no sense when applied to fossils or bacteria. In fact, there are more than 25 definitions of “species.” What definition is best? Coyne and Orr argued that, “when deciding on a species concept, one should first identify the nature of one’s ‘species problem,’ and then choose the concept best at solving that problem.” Like most other Darwinists, Coyne and Orr favor Ernst Mayr’s “biological species concept” (BSC), according to which “species are groups of interbreeding natural populations that are reproductively isolated from other such groups.” In Why Evolution Is True, Coyne explains that the biological species concept is “the one that evolutionists prefer when studying speciation, because it gets you to the heart of the evolutionary question. Under the BSC, if you can explain how reproductive barriers evolve, you’ve explained the origin of species.”42
Theoretically, reproductive barriers arise when geographically separated populations diverge genetically. But Coyne describes five “cases of real-time speciation” that involve a different mechanism: chromosome doubling, or “polyploidy.”43 This usually follows hybridization between two existing plant species. Most hybrids are sterile because their mismatched chromosomes can’t separate properly to produce fertile pollen and ovaries; occasionally, however, the chromosomes in a hybrid spontaneously double, producing two perfectly matched sets and making reproduction possible. The result is a fertile plant that is reproductively isolated from the two parents — a new species, according to the BSC.
But speciation by polyploidy (“secondary speciation”) has been observed only in plants. It does not provide evidence for Darwin’s theory that species originate through natural selection, nor for the neo-Darwinian theory of speciation by geographic separation and genetic divergence. Indeed, according to evolutionary biologist Douglas J. Futuyma, polyploidy “does not confer major new morphological characteristics… [and] does not cause the evolution of new genera” or higher levels in the biological hierarchy.44
So secondary speciation does not solve Darwin’s problem. Only primary speciation — the splitting of one species into two by natural selection — would be capable of producing the branching-tree pattern of Darwinian evolution. But no one has ever observed primary speciation. Evolution’s smoking gun has never been found.45
Or has it?
In Why Evolution Is True, Coyne claims that primary speciation was observed in an experiment reported in 1998. Curiously, Coyne did not mention it in the 2004 book he co-authored with Orr, but his 2009 account of it is worth quoting in full:
We can even see the origin of a new, ecologically diverse bacterial species, all within a single laboratory flask. Paul Rainey and his colleagues at Oxford University placed a strain of the bacteria Pseudomonas fluorescens in a small vessel containing nutrient broth, and simply watched it. (It’s surprising but true that such a vessel actually contains diverse environments. Oxygen concentration, for example, is highest on the top and lowest on the bottom.) Within ten days–no more than a few hundred generations–the ancestral free-floating ‘smooth’ bacterium had evolved into two additional forms occupying different parts of the beaker. One, called ‘wrinkly spreader,’ formed a mat on top of the broth. The other, called ‘fuzzy spreader,’ formed a carpet on the bottom. The smooth ancestral type persisted in the liquid environment in the middle. Each of the two new forms was genetically different from the ancestor, having evolved through mutation and natural selection to reproduce best in their respective environments. Here, then, is not only evolution but speciation occurring in the lab: the ancestral form produced, and coexisted with, two ecologically different descendants, and in bacteria such forms are considered distinct species. Over a very short time, natural selection in Pseudomonas yielded a small-scale ‘adaptive radiation,’ the equivalent of how animals or plants form species when they encounter new environments on an oceanic island.46
But Coyne omits the fact that when the ecologically different forms were placed back into the same environment, they “suffered a rapid loss of diversity,” according to Rainey. In bacteria, an ecologically distinct population (called an “ecotype”) may constitute a separate species, but only if the distinction is permanent. As evolutionary microbiologist Frederick Cohan wrote in 2002, species in bacteria “are ecologically distinct from one another; and they are irreversibly separate.”47 The rapid reversal of ecological distinctions when the bacterial populations in Rainey’s experiment were put back into the same environment refutes Coyne’s claim that the experiment demonstrated the origin of a new species.
Exaggerating the evidence to prop up Darwinism is not new. In the Galápagos finches, average beak depth reverted to normal after the drought ended. There was no net evolution, much less speciation. Yet Coyne writes in Why Evolution Is True that “everything we require of evolution by natural selection was amply documented” by the finch studies. Since scientific theories stand or fall on the evidence, Coyne’s tendency to exaggerate the evidence does not speak well for the theory he is defending. When a 1999 booklet published by The U. S. National Academy of Sciences called the change in finch beaks “a particularly compelling example of speciation,” Berkeley law professor and Darwin critic Phillip E. Johnson wrote in The Wall Street Journal: “When our leading scientists have to resort to the sort of distortion that would land a stock promoter in jail, you know they are in trouble.”48
So there are observed instances of secondary speciation — which is not what Darwinism needs — but no observed instances of primary speciation, not even in bacteria. British bacteriologist Alan H. Linton looked for confirmed reports of primary speciation and concluded in 2001: “None exists in the literature claiming that one species has been shown to evolve into another. Bacteria, the simplest form of independent life, are ideal for this kind of study, with generation times of twenty to thirty minutes, and populations achieved after eighteen hours. But throughout 150 years of the science of bacteriology, there is no evidence that one species of bacteria has changed into another.”49
40 Coyne, Why Evolution Is True, p. 116.
Darwin, The Origin of Species, Chapter IV (p. 70). Available online (2009) here.
H. B. D. Kettlewell, “Darwin’s Missing Evidence,” Scientific American 200 (March, 1959): 48-53.
41 Ernst Mayr, The Growth of Biological Thought (Cambridge, MA: Harvard University Press, 1982), p. 403.
Ernst Mayr, Populations, Species and Evolution (Cambridge, MA: Harvard University Press, 1963), p. 10.
Keith Stewart Thomson, “Natural Selection and Evolution’s Smoking Gun,” American Scientist 85 (1997): 516-518.
42 Jerry A. Coyne & H. Allen Orr, Speciation (Sunderland, MA: Sinauer Associates, 2004), p. 25-39.
Coyne, Why Evolution Is True, p. 174.
43 Coyne, Why Evolution Is True, p. 188.
44 Douglas J. Futuyma, Evolution (Sunderland, MA: Sinauer Associates, 2005), p. 398.
45 Wells, The Politically Incorrect Guide to Darwinism and Intelligent Design, Chapter Five (“The Ultimate Missing Link”), pp. 49-59.
46 Coyne, Why Evolution Is True, pp. 129-130.
47 Paul B. Rainey & Michael Travisano. “Adaptive radiation in a heterogeneous environment,” Nature 394 (1998): 69-72.
Frederick M. Cohan, “What Are Bacterial Species?” Annual Review of Microbiology 56 (2002): 457-482. Available online (2009) here.
48 Coyne, Why Evolution Is True, p. 134.
National Academy of Sciences, Science and Creationism: A View from the National Academy of Sciences, Second edition (Washington, DC: National Academy of Sciences Press, 1999), Chapter on “Evidence Supporting Biological Evolution,” p. 10. Available online (2009) here.
Phillip E. Johnson, “The Church of Darwin,” The Wall Street Journal (August 16, 1999): A14. Available online (2009) here.
49 Alan H. Linton, “Scant Search for the Maker,” The Times Higher Education Supplement (April 20, 2001), Book Section, p. 29.