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Summary of problems:Darwin's finches and peppered moths are unquestionably examples of natural selection. They are far from the only examples offered in biology textbooks.
Explore Evolution claims:
Biology textbooks cite two classic examples to support the claim that natural selection can produce small-scale change over a short time.
Campbell and Reece's Biology (6th edition) has a section in the chapter on evolution entitled, "Examples of natural selection provide evidence of evolution." It begins:
Natural selection and the adaptive evolution it causes are observable phenomena. As described in the interview at the beginning of this unit, Peter and Rosemary Grant of Princeton University are documenting natural selection and evolution in populations of finches in the Galápagos [Darwin's finches]. We will now look at two additional examples of natural selection as a pervasive mechanism of evolution in populations.
Those examples include the evolution of HIV and insects in response to drugs and insecticides, yet neither HIV nor insecticide even rates a mention in the index of Explore Evolution. In Chapter 9, Explore Evolution addresses antibiotic resistance, but only to discuss the origins of mutations conferring resistance, not to point out that natural selection is what causes that resistance to spread.
Sickle cell anemia also makes an appearance in Chapter 9, again purely as an example of a mutation. In Raven and Johnson's Biology (5th edition), however, it is the first example of natural selection described in the section entitled "Natural selection explains adaptive microevolution." Explore Evolution mentions that sickle cell anemia can be beneficial under some circumstances, but misses the chance to either discuss how natural selection makes it more common in human populations traditionally occupying malarial areas, or to employ a truly inquiry based approach by inviting students to develop and test hypotheses about malarial resistance in order to actually explore evolution.
Earlier, Raven and Johnson discuss examples of natural selection including its ability to maintain persistent latitudinal gradients in the oxygen-carrying hemoglobin molecule in ocean fish, differences which make northern fish more efficient in cold water and southern fish more efficient in warmer water. They also describe how selection improves the camouflage of butterfly caterpillars and allows snail populations to adapt to different local ground coloration, as well as pesticide resistance in tobacco budworms and agricultural weeds. Only later do they discuss industrial melanism in peppered moths or the beaks of Darwin's finches.
That introductory textbook authors tend to focus on a few common examples does not detract from the fact that natural selection is commonplace, easy to observe, and widely documented. Specialized textbooks on evolutionary biology present an even wider array of examples of natural selection. For instance, the chapter on natural selection in Futuyma's Evolutionary Biology discusses how selection produces a north-south gradient in the frequency of alleles of a certain gene in Drosophila flies, a pattern repeated on multiple continents. Similar patterns exist for field crickets. Later, Futuyma describes how guppies in streams without predators have brighter coloration than closely related guppies in streams with predators. In the example of snail shells also used by Raven and Johnson, Futuyma points to paleontological studies showing that the genetic polymorphism seen in the population today has persisted for thousands or millions of years — clear evidence of stabilizing selection — and studies of broken snail shells allow an evaluation of rates of predation on various color morphs — allowing an assessment of the selective pressures acting on the population.
The emphasis on two examples of natural selection, and the complete disregard for the myriad other examples in active use by introductory and advanced textbooks, reflects a common creationist strategy. Jonathan Wells, a creationist author at the Discovery Institute, has made a career of attacking the Galápagos finches and the peppered moth, perhaps in the belief that all of the other examples of natural selection would go away if he could disprove one or two well-known examples.
It is noteworthy that several figures in this chapter are drawn from Jonathan Wells' Icons of Evolution, a creationist work aimed at critiquing the content of common biology textbooks and common examples used to illustrate and explain evolutionary processes. While Wells is not credited in this chapter, many of the arguments are the same as in his earlier work (critiqued by NCSE's Alan Gishlick), as are the illustrations. Explore Evolution repeats many of the errors previously identified in Wells' work. Just as the authors of Explore Evolution have a well-documented religious agenda which belies the scientific appearance of their book, Wells is famous for his religious reasons for obtaining a PhD in biology and attacking evolution, rooted in his involvement with the Unification Church (better known as "Moonies"), led by Sun Myung Moon, or, as Wells refers to him, "Father":
I asked God what He wanted me to do with my life, and the answer came not only through my prayers, but also through Father's many talks to us, and through my studies.…
Explore Evolution, like Wells' earlier work, is rooted in a religious aversion to evolution, not in actual science. Scientists have sought to correct the erroneous claims displayed in Explore Evolution in their earlier incarnations, and the refusal to accept those corrections, or even to acknowledge those criticisms, recommends strongly against adopting this work into science classes.