many lines of evidence for evolution, and most of
my university students,who supposedly learned evolution
in high school, come to my courses knowing almost nothing
of this central organizing theory of biology.”
--Jerry A. Coyne; Why Evolution is True. 2009.
In my last blog entry, I gave an overview of the problems I heard in Glenn Beck's latest attack on the theory of evolution by natural selection. To recap briefly, those problems are errors in knowledge, distractability from the main point and reason for the discussion, and philosophical errors at the level of premises, reasoning and argumentation. The blog entry can be found here.
In this blog entry, I will discuss Glenn Beck's misapprehension of the modern theory of evolution because it is not even wrong. By this I mean that Beck's argument on his show, that evolution cannot be true because he has never seen a half-monkey, half human, is so off the mark that it is not even an argument. It is a straw-man, and does not rise to the level of an argument that can even be discussed. The phrase implies that even an argument that is wrong, would be better than this one.
What I am not going to do is try to convince anyone that the theory of evolution is true. I accept the evidence for evolution, which is so varied, so strong and so convincing that its reality is not even a casual discussion among biologists. However, there is so much evidence, on so many levels and coming from so many fields in the natural and physical sciences that it would take more than one book to recount it all. The interested reader can begin with Jerry Coyne's book, cited above, and continue with many well-written and documented books in the popular scientific literature. There is also another reason, and that is that is useless to argue either major or minor points of the theory, citing evidence, when the real problem is on a different level. That is, most people who refuse to accept the evidence for evolution by natural selection do so not because of this or that point has not been adequately addressed, but because he or she has a religious view of the world that includes biblical literalism, which is incompatible with most of modern science. Argumentation without a general agreement on world view is futile. And I believe that the problem is a political one and not scientific at all, and as a libertarian I do not believe that it is my place to use the force of law to change another's beliefs. I have written my opinion about the issue of evolution and science education here .
Glenn Beck's problem is not that he does not accept the evidence for the theory of evolution by natural selection. Although it is clear that he does not. His problem lies in that he attacked the theory citing a half-baked non-observation as evidence against it, and that indicated to anyone who knows the theory well that he does not know it or understand it in even the most rudimentary sense. This is not uncommon – as Coyne indicates in his book (quoted above). The purpose of this blog entry is not to change anyone's mind about evolution, but to discuss this common error that becomes the logical fallacy commonly called “the straw man argument” with amazing frequency.
The sum total of Glenn Beck's argument against evolution was that it was not likely to be true because , he said, “I haven't seen a half-person, half-monkey, yet.” When this statement came out of Beck's mouth, I shouted “Thank you, Bishop Wilberforce!” at the radio, because this was so reminiscent of the early arguments against evolution. From that time until this, the caricature of a blend of two species is, well, specious. It is a straw man put up in order to mock the opposition and to implant in the minds of listeners (or at least those who are ignorant of the actual theory of evolution) an idea that has never been a part of Darwin's theory of evolution by natural selection. Either Glenn was not paying attention during his high school biology class--a distinct possibility--or he is intentionally making a mockery of the theory in order to woo the most ignorant of his listeners. This second motive is also a possibility, however, it was not well-thought out, for in so doing he probably caused the majority of his listeners (including a NY News Tea Party reporter here) to do a double-take.
For those who have forgotten, or those who have never learned it, here is the theory of evolution by natural selection in a nutshell: The variation that we see among living organisms today arose gradually over time, brought about by a process called natural selection. There are five ideas that are necessary to any explanation of Darwin's theory and they are: evolution, speciation, the common ancestry of all life, natural selection, and gradualism. Evolution means change over time, and according to evolutionary theory, those changes in the genetic code of existing populations that create traits that give certain individuals a reproductive advantage – that is, traits that make it more likely for that individual to survive to reproduce – will become more common in the population over time. This change in the gene-frequencies of a population indicate that it is evolving.
Most of the time these changes in gene-frequencies occur naturally over time because successful reproducers pass those advantageous traits to their offspring, whereas those individuals who do not successful reproduce have no effect on the future genetic makeup of the population. This is natural selection*. Speciation usually occurs because enough variation occurs between two populations of the same species that they can no longer reproduce with one another. This is usually due to two populations being isolated from one another for some reason. Although speciation is arguably the most spectacular of the phenomena that the theory of evolution by natural selection explains, it is not the only one, or even the most common. But speciation is an effect of natural selection that has occurred many times over the history of life of earth, and that does mean that all species share a common ancestry; that is a link with every other species that is either a close relationship or a distant one, depending on how far back in the history of two species the divergence occurred.
*Although natural selection is by far the most common mechanism for evolutionary change in a population, it is not the only one: others such as gene-flow among populations, and the loss of genetic variation due to population bottlenecks and founder effect do have some influence.
For the purposes of our discussion about Glenn Beck's straw-man, the most important word in the paragraphs above is population. Populations evolve, individuals do not. That is because an individual's phenotype is fixed by the particular genotype he or she inherited. Some changes in gene expression do change over the lifetime, but an individual does not suddenly acquire half a genome from somewhere else. Therefore, one would not expect to ever see an individual that displays half the phenotype of one extant species and half the phenotype of another. Rather, if a biologist predicts that two species are closely related, she then expects to find many common traits between, and some important differences. Those common traits point to an ancestor species that is common to both of the related species. That ancestor species may or may not still be flourishing on earth. Extinction is also an important phenomenon that is predicted by the theory of evolution by natural selection.
With respect to human beings, monkeys do share common ancestry, which is indicated by enough common traits so that both monkeys and human beings are in the same taxonomic order: monkeys and humans are both primates. However, the most closely extant species to which humans are related are the great apes, all of whom are classified in the same taxonomic family – hominidae – which means “human-like”. The closest extant related species to humans is the chimpanzees. However, this does not mean that humans evolved from chimps. Nor does it mean that one should expect to find a half-chimp, half-person in the fossil record. Rather what we do find is that humans and chimps show a greater than 98% commonality in our genomes. We have enough traits in common to know that we had a common ancestor that walked the earth rather recently.
Another facet of Glenn Beck's mistake is that he equates some form of Lamarckism, the idea that evolution occurs by the passing of acquired traits to future generations through the genome, with Darwin's theory of evolution by natural selection. If this occurred, then one could say that individuals evolve. This is a philosophical mistake that Glenn actually shares with the communists, who promoted the neo-Lamarckian ideology proposed by Lysenko. This fallacy is necessary to the modern collectivists, but the Darwinian theory of evolution is not. Darwinisms is in fact at odds with it. But that discussion is part of the next blog entry on this topic. Stay tuned!