Tag Archives: mutation

The good doctor’s bad questions, cont’d.

Posted by Matt

PEPPERED MOTHS. Why do textbooks use pictures of peppered moths camouflaged on tree trunks as evidence for natural selection — when biologists have known since the 1980s that the moths don’t normally rest on tree trunks, and all the pictures have been staged?

This was something I didn’t know much about, but before I even did any research it struck me as dishonest to cite “staged textbook photos” as evidence to invalidate scientific studies. It turns out I was right: photoillustrations of the difference between peppered moth types are often staged with dead specimens to provide the clearest illustration of the point, but they don’t pretend to be from the original studies and experiments they are meant to illustrate.

Wells is referring to the English peppered moth Biston betularia. Until 1848, only light-colored individuals had been documented, but that year the first dark-colored carbonaria variant was recorded. By 1895, the percentage of the carbonaria variant was reported at 98%. The hypothesis for this was that the industrial revolution had coated previously light-barked trees with soot, giving dark moths better camouflage protection against predators. Evidence throughout the 20th century has supported this claim, but in the past two decades Bernard Kettlewell’s classic study has come under legitimate criticism for aspects of its design which may not have fully accounted for the diversity of moths’ daytime resting places.

However, between 2001 and 2007 Michael Majerus carried out a study that included moths found all over the tree (including the trunk, despite Wells’ claim) which nevertheless supported the differential camouflage theory. Much of creationists’ ammunition against the peppered moth as an example of natural selection comes from a review by Jerry Coyne of Majerus’ 1998 book Melanism: Evolution in Action. However, Majerus and others have stated that Coyne’s review misrepresents the book’s content, and Coyne himself has even expressed dismay that people have tried to use the article to argue against natural selection.

DARWIN’S FINCHES. Why do textbooks claim that beak changes in Galapagos finches during a severe drought can explain the origin of species by natural selection — even though the changes were reversed after the drought ended, and no net evolution occurred?

I should hope that the changes were reversed when conditions were reversed. Otherwise, that wouldn’t speak very highly of natural selection, would it? The thing is that evolution never stops. Whenever conditions change, new pressures cause different traits to be selected for. This “net evolution” business is misleading, and no one is citing this study as an example of new species creation. It is, however, a vivid example of natural selection at work.

MUTANT FRUIT FLIES. Why do textbooks use fruit flies with an extra pair of wings as evidence that DNA mutations can supply raw materials for evolution — even though the extra wings have no muscles and these disabled mutants cannot survive outside the laboratory?

Whether the flies in question are viable or not is not the point. These mutant flies are a simple and striking way to show that genetic mutations can produce radical changes in body plan and structure. Wells is missing the forest for the trees. The random nature of mutation suggests that most will be nonviable or at least nonadvantageous, as is the case here. Nevertheless, these dramatic mutations are evidence against the notion that mutation cannot produce enough change to generate new species.

HUMAN ORIGINS. Why are artists’ drawings of ape-like humans used to justify materialistic claims that we are just animals and our existence is a mere accident — when fossil experts cannot even agree on who our supposed ancestors were or what they looked like?

Phrases like “just animals” and “mere accident” seem intended to make people feel insulted by the theory of evolution, but that’s just one narrow-minded way to look at things. Drawings that appear in respected literature are scientific recreations based on fossils believed from the genus Homo and current knowledge about body plans and how vertebrate animals function. While there will continue to be debate over the details, there is little debate that these fossils represent our closest genetic relatives.

EVOLUTION A FACT? Why are we told that Darwin’s theory of evolution is a scientific fact — even though many of its claims are based on misrepresentations of the facts?

Damn scientific terminology to hell. For the last time, evolution is a scientific theory. The only things that are called facts in biology are observable data points. Theories are comprehensive and mechanistic explanations for how a process works. Gravity is the current accepted theory for why objects in the atmosphere fall to earth. Evolution is the current accepted theory for how species change in response to their environment and for how new species form. Both are based on a massive amount of evidence and are the best scientific explanations available for the facts at hand. I have yet to see any compelling scientific evidence that evolution misrepresents the facts.

While I was looking around online today i found this site, a point-by-point refutation of Wells’ book Icons of Evolution that covers a lot of the same ground I have here. I’m sure there’s tons of these things all over the internet, but like I said, I wanted to address these questions for my own satisfaction and to show that, to anyone with a working knowledge of the science, these questions are nowhere near the probing criticism of evolution that Wells wants them to be.


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