Saturday, November 21, 2009

In Defense of Darwin

One of the reasons why I started this blog was so that an open discussion could be had on evolutionary theory and Darwin himself. Mostly I intended this to focus on areas of theory within evolutionary biology, but also recognize that this could also be a tool for a clarification and explanation of evolutionary principles to a wider audience that could include scientists outside the field of biology and the public. To that end I’d like to respond to some comments that someone left in the blog about Darwin and evolution. I hope this individual does not take offense because I disagree, but at least welcomes the discussion that I will try to keep respectful.

“Of course most of (Darwin’s) initial observations have been disproved (for example his observation on black moths in England- now there are no black moths only white so his observations proved nothing more, or less, than it is easier to eat black moths on a white background and white moths on a black background...there is no evidence of macro evolution there)… I am a convinced micro evolutionist btw, on the macro level I see too many disconnects to fully accept his theory.”

If Darwin was mistaken in his early career, it was that it took him until the 1840’s before he came to the conclusion that the diversity of life was not a product of intelligent design, but that evolution proceeds by natural causes. He read the argument for design in the analogy of the watch by Paley (1809), and was influenced by him…early on. It may be easy to try to say that a scientist was wrong about certain things, especially early in his or her career. I don’t think that’s a very fair argument. I would be surprised if a young scientist was never wrong. And even if an old one was allegedly never wrong, I would find that highly suspect. The fact that remains is Darwin’s theory of evolution has not been falsified, which by definition continues to make it a viable theory. We have such an overwhelming evidence for biological evolution that we can characterize it as Ernst Mayr has as a description of a process in nature.

In terms of the scientific value of Darwin’s early work we can look to his first scientific book after his return from his voyage on the Beagle was centered on his observations of coral. He correctly recognized three stages of coral reef development: fringing reefs, barrier reefs, and atolls (1842). His initial hunch that artificial selection of domesticated animals and plants is a type of evolution that mirrors natural selection was correct. Sure Darwin wasn’t right about everything. Probably the worst theoretical misstep Darwin had was his theory of Pangenesis later in his career (1868) in which he incorrectly surmised a process for inheritance. But no reliable authority chides him for not knowing where the first step in natural selection, variation, comes from. It wasn’t until the rediscovery of Mendel’s work and the Modern Synthesis that a fuller understanding could be obtained. It remains that the majority consensus still rests in Darwin’s multi-component edifice for evolution (common decent, transmutation or speciation, uniformitarianism, and natural selection-Mayr 2001). It’s popular rhetorical device to take swipes at Darwin so that the full, perhaps unpalatable, implications of evolutionary theory are diminished if the founding father had flaws. Stephen Jay Gould in The Structure of Evolutionary Theory (2002) gives a very good account of this phenomenon:

“We must rank challenges by their degree of engagement with the Darwinian core; we cannot follow a strategy of mindless “raw empiricism” towards the Origin and simply compile a list of Darwin’s mistakes. All great works are bursting with error; how else could true creativity be achieved? Could anyone possibly reformulate a universe of thought and get every detail right the first time? “We should not simply count Darwin’s errors, but rather assess their importance relative to his essential postulates. (Consider, for example the standard rhetorical, and deeply anti-intellectual, ploy of politically motivated and destructive critics, American creationists in particular. They just list the mistakes, envelop each in a cloud of verbal mockery, and pretend that the whole system has drowned in this tiny puddle of inconsequential error.)”

I don’t know of any of Darwin’s errors that change the fact that he was correct in his core theories of the totality of evolution. But what about this business of industrial melanism being an error of Darwin’s? I wasn’t aware that Darwin was the first or at least early describer of industrial melanism. I did a little digging into the literature, and could find no direct reference that cites Darwin being involved in any of the early investigations. Steward (1977) states that although the first Biston betularia carbonaria (black phenotype with B. betularia typica being the white phenotype) was caught in Manchester, England in 1848, but wasn’t reported until 1864 by Edelston. After moving to Down House in the 1840’s Darwin rarely left predominantly due to ill health. His home was in the countryside. It is doubtful that Darwin observed industrial melanism, but may have heard about it. I would be interested in any references to that effect. Modern literature on the subject deals with bird predation of the peppered moth in industrial areas in England in the 1950’s (Kettlewell 1973).

I did some surfing on the internet and I did find information about industrial melanism. Interesting that many of the sites were creationist, and were attacking the example of industrial melanism as a textbook example of evolution. The two things that were continually repeated were that the research was a fraud because Kettlewell apparently glued dead moths to a tree for a photo that was published along with his paper. I am fairly certain that Kettlewell had no intention to deceive anyone by this act. It was simply a visual aid to show how well camouflaged the dark moths were. Remember his research took place in the 1950’s; and I imagine it would be very difficult to create a good resolution picture without immobilizing the subject. Besides the photo did nothing to falsify the observations of the original research, which subsequently was reproduced by others.

The other error in this comment was that if industrial melanism is discredited, then it’s not an example of macroevolution. First of all this “icon” of evolution was never intended to be an example of speciation. Industrial melanism has been cited in numerous biology textbooks rightly because it is an example of natural selection. There is a natural variability in phenotypic expression in peppered moths such that some moths were darker than others. Birds could not see the darker moths on soot-stained trees, and gobbled up the lighter colored moths. So dark moths were selected naturally. It’s a simple, elegant example of variation and selection, the core of Darwin’s theory. It’s popular in the creationist literature to try to make a distinction between micro- and macro-evolution with some accepting the former, but not the latter. The reason is simple. It’s virtually impossible to ignore the findings of modern molecular biology, which support evolution at the level of gene frequencies and genetic regulation that affects the phenotypically expressed individual, which is what is presented to the natural environment for selection. But creationists won’t accept phylogeny; that is they find it impossible to reconcile the biblical version of creation in which God created “kinds” of animals with Darwin’s alternative explanation, in which variation and selection results in adaptations and speciation. Morphological changes can accumulate as each successive species unfold in a lineage. Eventually these exhibit characteristics and morphological adaptations to allow the taxonomist to detect enough of a difference from that which has been previously described to feel that a new category is necessary. In the fossil record it is the descendent species from the earlier one that allows us to see that a new genera or family might have been initiated.

For creationists it’s harder to deny the findings of modern molecular biology in which a deluge of research findings indicate that natural selection chooses successful individuals that have a particular phenotype that can be demonstrated to have adaptive value. Populations beget others usually at the periphery of the species range. Once reproductively isolated, these are considered new species by definition. You might try to argue then that it’s as far as evolution can go. If you are intellectually committed to a sacred text that specifically states that all of life was created in a matter of days with each “kind” of creature being separately created, then it’s a lot harder to accept speciation and phylogeny. Perhaps you can accept speciation, but not phylogeny (macroevolution); then you are stuck, however, because once you accept the fact that speciation occurs, you don’t have to go any further intellectually to accept phylogeny. There are really no “kinds” of organisms. They are simply the current endpoints in lineages. Darwin showed us that evolution acts upon populations, not abstract essences that don’t exist in nature. There is no compelling indication that the evolutionary mechanisms found in microevolution cannot explain what is termed “macroevolution.” It’s the same process. This fact could be the subject of an essay in of itself, so I’ll move on.

“Well of course (Darwin’s) original theory is pretty well shot what we now have posited is Neo Darwin...but you know that I am sure.”

I’m not sure if our commentator is saying that Neo-Darwinism discredited industrial melanism, if it contradicts Darwin’s alleged observation of melanism, or if it supposed to negate all five sub-theories of evolution that are contained in Darwin’s “original theory.” I’ve already addressed the peppered moth specifically. The Modern Synthesis from which the Neo-Darwinist school sprung specifically vindicated Darwin. Yes that is the case. Scientists like Mayr, Simpson, and Dobzhansky reconciled the findings of the geneticists after Mendel’s work was rediscovered with natural selection. The secret of heredity was deciphered, and was identified as the source of variation on which selection acts. After 1859 some components of Darwin’s theory (common descent, speciation, diversification, and uniformitarianism) were accepted, but the mechanism of evolution, natural selection wasn’t accepted until the source of variation could be explained after the rediscovery of Mendel. Adaptations were thus explained, and were in total agreement with Darwin’s thesis. That’s why it is called the Modern Synthesis.

“Another interesting "fact" is a study done on the acceptance of Macro evolution as fact among scientists and engineers. The "soft' scientists (biologists chemists etc) are four to five more times as likely to accept macro evolution as fact than the hard scientists (engineers, physics, etc). What amazed the researchers (and I will point you to the study when I get a chance) was the relatively high number of scientist and engineers (most of these were the "hards") that did not accept Macro Evolution as fact. (I think it was almost 40% who considered themselves Evolutionary agnostics)”

I’m not sure that chemists would agree that they are “soft.” They are all about positing reaction mechanisms on the molecular level and testing their ideas statistically to determine if the proposed mechanism matches their predictions. Like wise I’m not so sure biologists would feel this way. Of course I have my own prejudices, and when I think of soft science I think of psychology and sociology, so perhaps shame on me. I’m not sure that the study specifically made the hard vs. soft distinction, but it does not surprise me at all that engineers or physicists are agnostic where evolution is concerned. Actually I take exception of the use of the term agnostic as it regards any scientific theory, because it implies that you can believe or disbelieve anything in science. In the analysis of data, evidence either supports a theory and therefore should be accepted, or does not support it and so should be rejected. Belief is irrelevant.

So I’m not surprised. If you move away from the field of evolutionary biology you very quickly find individuals who may not be aware of or understand how the evidences support evolutionary theory. Outside the circle of evolutionary biologists, physical scientists and the general public may have a hard time understanding how the actual natural history of organisms unfolded. Some engineers or physicists may have religious intellectual commitments that they can hold that aren’t inconsistent with their disciplines, while others scientists might simply have a problem with any science like biology or geology that to some extent relies on historical narrative. But let me make this perfectly clear. Biology is not (or at least is no longer) a soft science. Literature in biology is rife with statistical and computational analysis as in population biology. Darwinian evolution has not been falsified, and has been confirmed my multiple, independent lines of evidence from multiple fields of science. The argument that evolution is not empirical is a mischaracterization. To be sure not every field of science can be easily described by mathematics or amenable to laboratory investigation. But even in the laboratory we see that evolution has been vindicated in the form of “microevolution,” which explains phylogeny very well. To be sure it is extremely difficult to see new genera or families being born; such things could take thousands or millions of years. But we see changes in gene frequencies, we see how the phenotype is generated in ontogeny with variation on which selection acts, and we have morphological evidence from the study of extant and fossil species. Neo-Darwinism may even be considered to have hardened too much according to Steven Jay Gould.

In my previous essay, “How Can Evolution Inform Us in Predicting Extraterrestrial intelligence,” I discuss how it is predominantly astronomers, astrophysicists, and perhaps planetary scientists who may be assuming that intelligent life is rampant. I explain that a simplistic argument is employed and many have jumped on the bandwagon of egregious speculation. Not knowing how unlikely was the course of evolution that unfolded on our own planet was, somewhat wild speculation becomes the order of the day. Howard Gest of Indiana University says much the same thing. In his essay in the bulletin of the American Society of Microbiology (2005), he tells us that when he was asked to be on the Martian Meteorite Working Group organized by the Lunar and Planetary Institute in Houson, Texas after it was reported that the meteorite ALH4001 had potential signs of life, he found that he was the only biologist in attendance. So it may be easy for some scientist to be unsure of evolution if they haven’t consulted the proper authorities in biology or not have taken the time to really evaluate the wealth of evidence for evolution. That is truly soft thinking if there ever was.

Thanks to TIKTOK1984 for giving us something to talk about today. I’ve hoped that I’ve helped to clarify the matter from a biologist’s viewpoint.

Darwin, C. 1868. The Variation of Animals and Plants Under Domestication 2 vols. Murray, London.

Gest, H. 2005. “Microbes in the Search for Extraterrestrial Life.” ASM News 71:12 pp.560-561.

Gould, S. J. 2002. The Stucture of Evolutionary Theory. Belknap Press, Cambridge.
p. 168.

Kettlewell, B. 1973. The Evolution of Industrial Melanism. Clarendon Press.

Mayr, E. 2001. What Evolution Is. Basic Books, New York. p. 86.

Paley, W. 1809. Natual Thology: Or Evidences of the Existence and Attributes of the Deity. J. Faulder, London.

Steward, R.C. (1977). "Industrial and non-industrial melanism in the peppered moth Biston betularia (L.)", Ecological Entomology 2 (pp. 231–243).


  1. "The "soft' scientists (biologists chemists etc) are four to five more times as likely to accept macro evolution as fact than the hard scientists (engineers, physics, etc)."


    Oh dear. That quote made me sad. What is it that makes physics 'harder' than biology? Where does chemical engineering fit in? The quoter seems to have this idea that physicists are more 'intelligent' than biologists and that is what makes him feel that if 'intelligent' people think evolution isn't right well then it can't be!

    Take away the perceived superiority of physicists and all that quote says is "people who haven't studied evolution are less likely to agree with it" which is hardly ground breaking.

    Love your blog, btw :)

  2. Thanks for the kind word, LR. I'm doing this just for you (or someone just like you).