Evolution Icon Evolution

A Solid 10: Concluding My Review of Massimo Pigliucci’s Treatment of Jonathan Wells’s Icons of Evolution

Pigliucci.jpgI’ve been reviewing philosopher Massimo Pigliucci critique, in his 2002 book Denying Evolution: Creationism, Scientism, and the Nature of Science, of Jonathan Wells’s Icons of Evolution. Icon by icon, let’s continue (please also see my earlier two posts here and here).

Icon 8: Four-Winged Fruit Flies
Pigliucci doesn’t contest Wells’s critiques of the treatment of four-winged fruit flies. Instead he states that, “Only a few misguided molecular biologists (ignorant of evolution)” have claimed that “There are no known beneficial morphological mutations.” (Denying Evolution, p. 257) One would therefore expect Pigliucci to give examples of such, and he thinks he does. He writes: “There are countless examples of beneficial morphological and behavioral mutations in the technical literature.” (p. 257) No citation is given. He goes on: “If he would only stop and think for a second, Wells would realize that he carries many of these mutations himself, which is in part why he looks different from other human beings.” (p. 257)

Here Pigliucci is begging the question. No one contests that human beings have genetic differences from other species that give us our unique body plan and intellectual abilities. The question is whether random mutations can produce the kinds of changes in organisms necessary to create new body plans. Wells points out that creating four-winged fruit flies requires multiple mutations, and even then they lack flight muscles. This implies that multiple coordinated mutations are necessary to build new body plans. It would help Darwinian theory to provide evidence of mutations radically changing body plans. Pigliucci must provide this evidence, and not just assert that it exists. He thinks he can provide this evidence, and here’s the example he gives:

A typical example of a morphological mutation that is beneficial (conditionally on the specific environment encountered by the organism) is the change in skin coloration that has happened several times during the course of human evolution. (Denying Evolution, p. 257)

Pigliucci is apparently aware that increased (or decreased) melanin in the skin of humans simply means producing more (or less) of something you already can produce. He seems to anticipate that this might not be considered by Wells to be a “morphological mutation.” He thus writes: “this example also shows that the distinction that Wells makes between morphological and biochemical mutations is entirely artificial; the morphological mutations that affect the color of the skin are in fact biochemical mutations that change the rate of production of the skin’s pigment, melanin.” (Denying Evolution, pp. 257-258) Pigliucci simply asserts that this is a “morphological mutation” even though what Wells means is a mutation capable of changing the organism’s body plan. Wells explains that he’s looking for mutations that show “large-scale variation” which produce “a gain of structures” that can “supply the raw materials for morphological evolution.” (Icons, pp. 177, 186-187, 188) Can changes in skin color provide this large-scale variation and gain of new structures required for morphological evolution? Of course not. In fact, it’s noteworthy that when evolutionary biologists try to show how developmental mutations can lead to evolution, they often involve small-scale changes in coloration.

Stephen Meyer notes this in Darwin’s Doubt. He observes that the National Center for Science Education (NCSE) cited a paper in the Proceedings of the National Academy of Sciences USA to show the power of evo-devo to explain morphological evolution. He writes:

The paper did not show what the NCSE claimed, however. It did assert that changes in regulatory DNA produce “both relatively modest morphological differences among closely related species and more profound anatomical divergences among groups at higher taxonomical levels.” But the study only showed how changes in the cis-regulatory elements in fruit fly DNA might have affected the coloration of wing spots in several different types of flying insects. It did not report any significant change in the form or body plan of these insects. Instead, the study highlighted a clear case of a viable mutation generating merely a minor or superficial change. (Darwin’s Doubt, p. 317)

The same critiques could be made here: If changing the skin color in human beings amounts to the kind of “morphological mutation” that can fundamentally change the body plan or lead to new species, then Massimo Pigliucci must believe that human individuals with different skin pigments are like different species in the wild. I certainly don’t believe this is the case, and I strongly doubt that he does either.
In any case, if changes in pigment levels in humans — which he admits merely “change the rate of production of the skin’s pigment, melanin” (i.e., changing the rate at which you produce something you already have) — is his best example of a “morphological mutation,” we can rest assured that evolutionary biology cannot provide the kind of morphological mutations Wells is looking for.

Icon 9: Horses
Pigliucci claims that Wells “acknowledges that the current view of the evolution of horses is very likely to be correct” (p. 258), not noting that Wells discusses chronological inversions that afflict the horse series. But it also seems that Pigliucci doesn’t contest Wells’s central claim that Darwinian evolution implies materialistic conclusions. Pigliucci concedes, “General statements by evolutionary biologists that natural selection is a purposeless and directionless process are consistent with the evidence, since nobody has been able to demonstrate either a purpose or a direction in it.” (p. 258) Pigliucci plainly states: “There is simply no empirical evidence … to support either purpose or direction in nature.” (p. 258) So what is wrong with Wells’s claim? According to Pigliucci, the materialistic assumption that evolution is purposeless and directionless “has worked very well in practice, and Wells provides no reason to abandon it.” (p. 258) Except, I suppose, for all of the evidence Wells has shown throughout his book that the evidence does not support the claims of neo-Darwinian theory.

Icon 10: Human Evolution
Here, Pigliucci acknowledges that Wells is correct that the Piltdown story was a hoax, but once again the only point he can make is that the “hoax was actually uncovered by evolutionary biologists, not creationists.” (Denying Evolution, p. 258) I don’t know if his claim is true, but once more, what matters isn’t who made a discovery but whether the discovery is true. Yet again, Pigliucci is committing the genetic fallacy, suggesting that the truth of a claim depends on who is making it. Pigliucci then claims that Wells “admits in his book, the hominid fossils discovered after Piltdown are genuine and do show intermediate stages of human evolution.” (p. 259) I’ve looked through Chapter 10 of Icons of Evolution and I can find no such admission. Instead, I see Wells stating the following — written in the subjunctive:

In the twentieth century, the ultimate icon seemed to acquire the evidence it initially lacked. Numerous fossil discoveries supplied what appeared to be transitional links in the evolutionary chain leading to modern humans; experiments on peppered moths and other organisms seemed to provide the missing evidence for natural selection; and geneticists thought they had found the raw materials for evolution in DNA mutations. (Icons, p. 211)

Now we already know that Wells doesn’t believe that the peppered moth or similar stories provide evidence for natural selection. Nor does he think that geneticists have discovered raw materials for evolution in DNA mutations. Thus, given Wells’s use of subjunctive, it’s safe to assume he also doesn’t really think that fossils have shown the “transitional links” leading to modern humans. The rest of the chapter bears this out. He notes that supposed intermediate fossils have been called “bones of contention” where “each new discovery seems to add to the problem rather than alleviate it.” (Icons, p. 218) Wells challenges the idea that one can show human evolution using fossils — and he certainly doesn’t make the concessions Pigliucci claims he does. In any case, for a lengthy discussion of how the fossil evidence doesn’t support human evolution from ape-like creatures, see our book Science and Human Origins.

Pigliucci closes by acknowledging “the abysmal state of the textbook publishing industry.” He agrees that biology textbooks can contain “mistakes and inaccuracies.” (Denying Evolution, p. 259) Having reviewed his treatment of Jonathan Wells’s book, I can’t find a single legitimate problem that Pigliucci has identified with Icons of Evolution. Instead, I see that Pigliucci has conceded that many of Wells’s complaints about biology textbooks are valid, including Wells’s central point that textbooks can be highly inaccurate. When Pigliucci disagrees with Wells, he repeatedly puts words in in the latter’s mouth and cites evidence or data that doesn’t actually refute Wells’s argument. The icons of evolution remain problems for Darwinian theory, some 14 years after Jonathan’s book was written. Icon by icon, I would say that makes a solid, if not a perfect ten.

Casey Luskin

Associate Director and Senior Fellow, Center for Science and Culture
Casey Luskin is a geologist and an attorney with graduate degrees in science and law, giving him expertise in both the scientific and legal dimensions of the debate over evolution. He earned his PhD in Geology from the University of Johannesburg, and BS and MS degrees in Earth Sciences from the University of California, San Diego, where he studied evolution extensively at both the graduate and undergraduate levels. His law degree is from the University of San Diego, where he focused his studies on First Amendment law, education law, and environmental law.



__k-reviewIcons of EvolutionMassimo Pigliucciphilosophyscience