Icon of Obfuscation

Jonathan Wells' book Icons of Evolution and why most of what it teaches about evolution is wrong

By Nic Tamzek [1]

Version 1.0
[Last Modified: November 24, 2002]

Posted May 26, 2003


  1. Introduction
  2. A chapter-by-chapter critique of Icons of Evolution:

  3. Chapter 2: The Miller-Urey experiment
  4. Chapter 3: Darwin's Tree of Life
  5. Chapter 4: Homology in Vertebrate Limbs
  6. Chapter 5: Haeckel's Embryos
  7. Chapter 6: Archaeopteryx -- The Missing Link
  8. Chapter 7: Peppered Moths
  9. Chapter 8: Darwin's Finches
  10. Chapter 9: Four-Winged Fruit Flies
  11. Chapter 10: Fossil Horses and Directed Evolution
  12. Chapter 11: From Ape to Human: The Ultimate Icon
  13. Conclusions
  14. Acknowledgements
  15. References
  16. Endnotes

1. Introduction

Jonathan Wells' book Icons of Evolution: Science or Myth? Why Much of What We Teach About Evolution Is Wrong (henceforth Icons) makes a travesty of the notion of honest scholarship. Purporting to document that "students and the public are being systematically misinformed about the evidence for evolution," (p. XII) via common textbook topics such as peppered moths, embryo similarities, and fossil hominids [2], Icons in fact contains a bevy of its own errors. This is not original -- creationists have been making mistakes about evolution for years. Newly and more insidiously, however, Icons contains numerous instances of unfair distortions of scientific opinion, generated by the pseudoscientific tactics of selective citation of scientists and evidence, quote-mining, and "argumentative sleight-of-hand," the last meaning Wells' tactic of padding his topical discussions with incessant, biased editorializing. Wells mixes these ingredients in with a few accurate (but always incomplete) bits of science and proceeds to string together, often in a logically arbitrary fashion, a narrative that is carefully crafted to make the semblance of an honest case for Wells' central defamatory accusation: that mainstream biologists are "dogmatic Darwinists that misrepresent the truth to keep themselves in power" (pp. 242-243).

This essay will show that it is Wells' book Icons that is shot through with misrepresentations.

The central pillar of Wells' case is this:

"Some biologists are aware of difficulties with a particular icon because it distorts the evidence in their own field. When they read the scientific literature in their specialty, they can see that the icon is misleading or downright false. But they may feel that this is just an isolated problem, especially when they are assured that Darwin's theory is supported by overwhelming evidence from other fields. If they believe in the fundamental correctness of Darwinian evolution, they may set aside their misgivings about the particular icon they know something about." (Icons, pp. 7-8)
In other words, Wells argues that the specialists know about the problems in their field of expertise, but that everyone thinks that the evidence supporting evolution is somewhere else. This is just plain false, as we shall see -- the experts in each field have explicitly stated that the evidence in their field supports evolutionary theory, and further they have supported their statements with evidentiary arguments. If Wells' contention about the experts is false, then Wells' argument collapses. Wells likes asking questions; it is now time for him to answer some.

2. Chapter 2: Miller-Urey experiment

Prebiotic Oxygen

A key question in origin-of-life research is the oxidation state of the prebiotic atmosphere (the current best guess is that the origin of life occurred somewhere around 4.0-3.7 bya (billion years ago)). Wells wants you to think that there is good evidence for significant amounts free oxygen in the prebiotic atmosphere (significant amounts of free oxygen make the atmosphere oxidizing and make Miller-Urey-type experiments fail). He spends several pages (14-19) on a pseudo-discussion of the oxygen issue, citing sources from the 1970's and writing that (p. 17) "the controversy has never been resolved", that "Evidence from early rocks has been inconclusive," and concluding that the current geological consensus -- that oxygen was merely a trace gas before approximately 2.5 bya and only began rising after this point -- was due to "Dogma [taking] the place of empirical evidence" (p. 18). None of this is true (see e.g. Copley, 2001).

Why does Wells leave out the converging independent lines of geological evidence pointing to an anoxic early (pre ~2.5 bya) atmosphere?

Was the prebiotic atmosphere reducing? Are the Miller-Urey experiments "irrelevant"?

The famous Miller-Urey experiments used a strongly reducing atmosphere to produce amino acids. It is important to realize that the original experiment is famous not so much for the exact mixture used, but for the unexpected discovery that such a simple experiment could indeed produce crucial biological compounds; this discovery instigated a huge amount of related research that continues today.

Now, current geochemical opinion is that the prebiotic atmosphere was not so strongly reducing as the original Miller-Urey atmosphere, but opinion varies widely from moderately reducing to neutral. Completely neutral atmospheres would be bad for Miller-Urey-type experiments, but even a weakly reducing atmosphere will produce lower but significant amounts of amino acids. In the approximately two brief pages of text where Wells actually discusses the reducing atmosphere question (p. 20-22), Wells cites some more 1970's sources and then asserts that the irrelevance of the Miller-Urey experiment has become a "near-consensus among geochemists" (p. 21).

None of this is meant to convey the impression that no controversies exist (both Cohen (1995) and the Davis and McKay (1996) article cited by the above-quoted Kral et al. (1998) are about the various competing hypotheses about the origin of life). But textbooks generally mention some of these hypotheses (briefly of course, as there is only space for a page or two on this topic in an introductory textbook), and furthermore generally mention that the original atmosphere was likely more weakly reducing than the original Miller-Urey experiment hypothesized, but that many variations with mildly reducing conditions still produce satisfactory results. This is exactly what is written in the most popular college biology textbook, Campbell et al.'s (1999) Biology, for instance. In other words, the textbooks basically summarize what the recent literature is saying. The original Miller-Urey experiment, despite its limitations, is also repeatedly cited in modern scientific literature as a landmark experiment. So why does Wells have a problem with the textbooks following the literature? Wells wants textbooks to follow the experts, and it appears that they are.

The RNA world

Wells writes (p. 22) as if the RNA world is an alternative to failed Miller-Urey-style experimentation. He cites no source for this claim, because the claim is pure obfuscation.

3. Chapter 3: Darwin's Tree of Life

Wells mixes up several issues in this chapter. As we saw in the previous chapter, he will give several topics each a cursory and incomplete treatment, raising doubts about each subject and connecting them together whether they are logically connected or not.

The Cambrian Explosion

Here Wells is running down a path well-worn by his creationist and 'designist' (IDist) colleagues. As a result there is already significant literature available on the "animal phyla appeared suddenly, and without precursors, and all equally far apart from each other"-sort of contention.

Molecular Phylogeny

Wells' second argument against the Tree of Life deals with the 'molecular clock' hypothesis -- namely that DNA or protein sequence divergence is regular enough to date ancient splits between lineages. This hypothesis is indeed being questioned by scientists, as the influence of things like natural selection may well alter the rate of sequence change (e.g. cone snail venoms are a fantastic example of rapid sequence divergence under selective pressure; see Espiritu et al., 2001). And if these changes occur often enough then getting accurate clock dates, particularly for distant events, will be very hard. This is an entirely different thing from determining molecular phylogenies, however, which is what Wells is actually trying to debunk. But unfortunately for Wells, there is considerable evidence that these phylogenies are reliable and in reasonably good accord with phylogenies generated from other data. On the general subject of accuracy in molecular phylogenies see Theobald 2002b and for recent work on phyla evolution and metazoan molecular phylogenies, which are quite certainly not in crisis, see recent articles in places Evolution and Development (e.g., Collins and Valentine, 2001; Peterson and Eernisse, 2001).

The Root of the Tree of Life

The 'Tree of Life' is the idea, most famously advocated by Darwin, that all known life is descended from a common ancestor and is connected by a phylogenetic 'tree':

"The affinities of all the beings of the same class have sometimes been represented by a great tree. I believe this simile largely speaks the truth. The green and budding twigs may represent existing species; and those produced during each former year may represent the long succession of extinct species. ... As buds give rise by growth to fresh buds, and these, if vigorous, branch out and overtop on all sides many a feebler branch, so by generation I believe it has been with the great Tree of Life, which fills with its dead and broken branches the crust of the earth, and covers the surface with its ever branching and beautiful ramifications." (Darwin, Origin of Species)

This idea has recently been implemented on the web in a splendid fashion. See the Tree of Life Web Project Home Page.

In Icons, Wells has a ball with recent scientific debates over whether or not lateral gene transfer mixed up ancient genomes so much that deepest branches of the tree are mixed up. Basically, some scientists have proposed that the idea of a single "last common ancestor" should be replaced with the idea of a "last common gene pool" that the extant three domains of of life -- eukaryotes, archaea and eubacteria, in one classification scheme -- gradually emerged from. Carl Zimmer (2001) describes this as the 'Mangrove of Life' idea. Wells (of course) milks this for all it's worth, proclaiming the downfall of common descent and the 'uprooting of the tree' and whatnot, but he is distorting things.

The Chinese paleontologist story

On the last page of this chapter of Icons (p. 58), Wells recounts his story of an unnamed Chinese paleontologist who visited the U.S. in 1999 and who Wells quotes as saying, "In China we can criticize Darwin, but not the government; in America, you can criticize the government, but not Darwin." Given past experience with antievolutionist anecdotes, it is to be strongly suspected that there is more to this story than Wells is telling us.

4. Chapter 4: Homology in Vertebrate Limbs

Is the definition of homology circular?

Wells spends this entire chapter thoroughly confused about homology, and does his best to confuse his readers as well. About five minutes of research by yours truly turned up a perfectly reasonable discussion of homology (Amundson, 2001) which nicely straightens things out: in a nutshell, homology is detailed similarity of organization that is functionally unnecessary, meaning the similarity is unnecessary (the trait in question may be, and usually is, functional).

This is not a drastically complicated idea, but Wells is able to confuse himself because post-Darwin, homology is usually defined as 'A feature in two or more taxa is homologous when it is derived from the same (or a corresponding) feature of their common ancestor.' Wells accuses scientists of making the definition circular and assuming common descent rather than providing evidence for it, but of course if you doubt common descent then you have to go back to the original definition, wherein you have peculiar similarities that are functionally unnecessary staring you in the face, begging you for an explanation. Amundson (2001) critiques the circularity charge well:

This criticism relies on a faulty view of what scientific definition amounts to. A scientific definition is not a semantic stipulation that creates an analytically true statement (i.e. a statement the denial of which is self-contradictory). Rather, a scientific definition typically states a property that is considered to be the most deeply explanatory of the phenomena that are central to the term being defined. Lankester and Mayr consider ancestry to explain patterns of homology, and stress that fact by making it the definition. The historical definition is not viciously circular as long as homologies can be recognized and picked out by criteria other than common ancestry. It is an empirical fact that homologies (as picked out by the criteria below) are arranged among organisms in a pattern that is explainable by common ancestry, and independent evidence from various fields supports common ancestry as a historical fact.

Complexities of Homology; R. A. Raff comments

On pp. 72-78, Icons cites Rudolf Raff and other scientists in an attempt to build a case that the use of homology is somehow in crisis. The reality of most of these cases is that scientists are simply discovering that different kinds of homology are found at different phylogenetic and organizational levels. Over the last few years, the growing synthesis of evolutionary biology and developmental biology has created a hot new subfield referred to as "evo-devo." For an introduction to evo-devo, see the article "The evolution of evo-devo biology," which heads up an entire special issue on the topic that was published freely on the web by the journal Proceedings of the National Academy of Sciences (PNAS).

The evo-devo specialist Rudolph Raff recently (Nov.-Dec. 2001) wrote an editorial in the journal Evolution and Development entitled "The creationist abuse of evo-devo," specifically on Wells and his book Icons. Raff writes, in part,

Icons of Evolution presents the dark view of evolutionary biologists held by Wells. He says that we are involved in a conspiracy to consciously lie in what we teach students and present in our writings. Claims of deliberate scientific fraud and "Darwinian censorship" reaches a crescendo as the book progresses. These are strong accusations built on a shaky scaffolding of special pleading and deceptive use of quotations. [...] Wells notes correctly that there is not a necessary connection between homologous genes and homologous structures, nor must homologous structures arise from similar developmental processes. [Wells and colleagues conclude that...] "naturalistic mechanisms proposed to explain homology do not fit the evidence." What logical gymnastics! If it is unexplained, it must be unexplainable by evolutionary biology. If it's be unexplainable by evolutionary biology, it must require an intelligent designer. Unfortunately, as the influence of the intelligent designer grows in this train of thought, the relationships between phenomena and explanations becomes increasingly arbitrary. Finally one reaches a point where all biological features are "special creations" and other explanations become unnecessary. (Raff, 2001)

For a very detailed introduction to dozens of detailed homologies (none mentioned by Wells except the vague 'similarity' idea) within the chordates that have been discovered via comparative biology, see this webpage on Chordate Anatomy and Evolution).

5. Chapter 5: Haeckel's Embryos

In the interests of forthrightness, one point must be conceded straight out: Haeckel's embryo drawings have no place in textbooks except as an example of how erroneous ideas can get tacked onto important truths and perpetuated even after being debunked (Haeckel's inaccurate drawings have actually been 'exposed' multiple times since the 1800's, the Richardson et al. (1997) article that Wells cites being only the most recent example). However, Wells as usual exaggerates the implications of this for evolution.

6. Chapter 6: Archaeopteryx: The Missing Link

Archaeopteryx has long been something that creationists have felt the need to deal with somehow, as it is a clear fossil intermediate between two vertebrate classes. However, creationist claims have been refuted so often and so thoroughly regarding Archaeopteryx that very little remains for Wells to do except raise a smoke screen over whether or not Archaeopteryx was the actual species through which the genes of the last common ancestor of modern birds passed, or whether it was a closely related side-branch. Either way, it is clear evidence that a transition between the classes occurred.

7. Chapter 7: Peppered Moths

So many things are wrong with Wells' treatment of peppered moths (Biston betularia) that it is hard to list them all; but I will try. The authoritative reference on this topic is M.E.N. Majerus' 1998 book Industrial Melanism: Evolution in Action. This book includes two long chapters on Biston. The first chapter, "The peppered moth story," recounts the basic story of melanism in Biston, and relates how this story was pieced together by Kettlewell and others. The second chapter, "The peppered moth story dissected," gives a thorough critical review of the basic story, considering aspects and details of the basic story in the light of research (by Majerus and others) post-dating Kettlewell.

Crucially, however, Majerus clearly and explicitly concludes that, in his view, Kettlewell got things basically correct. At the beginning of his second peppered moth chapter, Majerus writes,

First, it is important to emphasize that, in my view, the huge wealth of additional data obtained since Kettlewell's initial predation papers (Kettlewell 1955a, 1956) does not undermine the basic qualitative deductions from that work. Differential bird predation of the typica and carbonaria forms, in habitats affected by industrial pollution to different degrees, is the primary influence of the evolution of melanism in the peppered moth (Majerus, 1998, p. 116).

Majerus is so clear on this point that one suspects that he was anticipating that his critique would be misinterpreted by non-peppered moth researchers. It seems that there is a "too good to be true" quality about the peppered moth story that leads people to interpret any hint of criticism as a sign that the whole basic story is crashing down. Scientists are by no means immune to this tendency, and indeed they may be more prone to it given the regularity with which popular ideas have been overturned throughout the history of science. The press has an even greater tendency towards snap judgements and oversimplifications when it comes to scientific discussions. Antievolutionists, on the other hand, have always been stuck muttering "it's just microevolution within a species." While this is true, the rapidity and obvious adaptiveness of the change effected by natural selection still seemed to give antievolutionists discomfort. Therefore, it is understandable that when Wells and his fans sniffed a scientific controversy over peppered moths (in truth it was a fairly marginal kind of controversy), they blew things way out of proportion.