Dec 18 2007
Evolution News & Views is the propaganda blog for the misnamed Discover Institute, the also misnamed “think tank” for intelligent design (ID). I only occasionally bother to correct the nonsense spewing forth from that institution, lest I risk being sucked into a bottomless pit of logical fallacies and misinformation. But this recent blog entry by Casey Luskin caught my attention, partly because it is a good example of sloppy thinking but also because I predicted that exactly such an argument would soon appear on this blog.
On a recent episode of the Skeptics Guide I mentioned that the press release for this study of St. Barnard evolution was one of the silliest and most irresponsible science press releases I have seen. It said that the study looking at the morphological change in St. Barnards over time “cast doubt on the theory of creationism.” This is like saying that new satellite measurements of the earth cast doubt on the flat earth theory. First, creationism is not a theory and did not deserve to even be mentioned, and second the press release failed to even point out exactly how this new evidence even related to evolutionary theory. I predicted the ID crowd would exploit the careless press release to take a jab at evolutionists, and I was right. Luskin directly writes:
Moreover, if there’s no scientific controversy over intelligent design, then why are these researchers touting how their “St. Bernard study casts doubt on creationism”?
Luskin’s criticisms are not legitimate – it is, rather, and example of the primary problem with ID proponents: they are intellectually dishonest and/or incompetent. It’s hard to tell what mix of these two traits they represent, but the nature of their arguments demonstrates that they cannot be both honest and competent.
The new evidence shows that the St. Barnard of today shows morphological differences from specimens of up to 120 years ago. The differences are due to artificial selection -the selection of breeders acting on variation within the breed. This, of course, is not evidence for evolution through natural selection. But it does demonstrate one important and relevant principle – that a population can change is morphological characteristic in a directed fashion under selective pressures. Selection acting on variation can produce directed change – evolution.
Luskin, in an attempt to distract and confuse, completely distort the implications of this evidence and the claims being made for it. He writes:
“Breeders selected” and “the selective considerations of breeders” sure sound a lot like intelligently-guided artificial selection, not natural selection. But these scientists don’t let little distinctions like that get in the way of finding support for Darwinism. In fact, they claim their research demonstrates the grand Darwinian narrative: “this research once again demonstrates how selection – whether natural or, in this case, artificially influenced by man – is the fundamental driving force behind the evolution of life on the planet.” So intelligent design is now cited as proof that natural selection is the fundamental driving force behind the evolution of life.
Notice the legerdemain – he craftily inserts the phrase “intelligently-guided” before “artificial selection” so as to lay the groundwork for his big conclusion: that change over time through artificial selection is “intelligent design.” Wow – nicely done! What Luskin is saying is that artificial selection is more analogous to intelligent design (the design and creation of a creature wholesale from the ground up) than to evolution through natural selection.
I cannot read such patently absurd distortions without asking myself – does this guy really believe this?
Next Luskin argues that the history of dog breeding is evidence against evolution. He quotes text from Explore Evolution (more anti-evolution propaganda – promoting the notion of a genuine scientific controversy where none exists)
[A]s different as these [dog] breeds are, the differences still fall within limits. No one has ever bred a dog lighter than a few pounds, or heavier than about 150 pounds, despite thousands of years of selective breeding.
The claim is factually incorrect – St. Barnards range up to 200 pounds, and the world’s largest dog, a Mastiff, weighed in at 282 pounds (it is likely not a coincidence that the error significantly underestimated variation among dog breeds). Luskin is therefore claiming that a 100 fold difference in weight between the smallest and largest dogs is evidence for the limits, rather than the power, of selection. It is very relevant that historically we have documented the evolution through artificial selection of dogs from a single wolf-like breed to the hundreds of breeds extant today as different as chihuahuas and mastiffs.
Worse, the argument betrays fundamental misunderstandings about evolution. Of course there are limits to the changes that any breeding program can create. As evolution progresses over time species tend to become more and more constrained. Stephen J. Gould described this in his book Wonderful Life. Disparity among species tends to decrease over time, even as diversity tends to increase. All mammals will always be more similar to each other (less disparity) than any of them are to reptiles. There is less disparity among carnivores than among mammals, and even less among dogs than among all carnivores. Dogs will always retain a certain “dogginess” even as diversity among dog breeds increases.
What this means is that a dog will never evolve into a cat. It also means that there are limits to how much change selection acting on variation can create in a constrained species.
Also, Luskin is making assumptions about how much disparity should be possible within a few thousand years. I don’t know of anyway to estimate this – it seems like this would be the result of chaotic variation. It also seems to me that a 100 fold disparity in size by weight is pretty significant. Luskin seems to be arguing that the fact there are no dogs the size of elephants somehow casts doubt on evolution.
This brings up another common ID misunderstanding of evolution – that it theoretically should be able to result in any outcome, and therefore the failure to create a certain outcome casts doubt on the theory. But again, this is absolutely not true. Evolutionary history constrains the possible outcomes. It is also limited to naturally occurring variation. Selection (natural or artificial) can only act upon the variation that comes into existence through mutations and recombination (mixing of genes). Recombination can be influenced to some degree by selective breeding, but not mutations.
There is therefore a random element to the direction of evolution. It may be that significantly larger breeds of dogs are yet to come, but perhaps it will have to wait for a fortuitous mutation or combination of genes to occur.
Luskin is arguing that something which has not happened (to some arbitrarily sufficient degree) in one species in a few thousand years is therefore not possible, even given millions of species and millions of years.
This episode demonstrates the need for scientists and science press writers to be careful and responsible in how they explain and report science to the public. Sloppy reporting will just feed the pseudoscientists. It also demonstrates that there is apparently no limits to the misinformation and distortions that ID proponents are willing to commit in furthering their ideology.
The combination just creates a mess that somebody has to clean up.
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