Moths & Men

Those Peppered Moths

The Peppered Moths of the area near Manchester, England hold a special place in the history of Darwin’s theory of evolution. He doubted that evolution by natural selection would ever be observed in the wild – it would be just too difficult to find it and it would happen too slowly. These moths seemed to prove him wrong and to give a huge boost to his theory when it needed one most, at the end of the 19th century.

In the 1890s and early 20th century, Darwin’s theory was under attack by people who had discovered Mendel’s ideas on genetics – totally unknown to Darwin because they were published and then forgotten for a generation or so – and by other evolutionists who favored Lamarckian ideas or more mystical fare. The idea of evolution itself wasn’t in danger of abandonment, but the mechanism, was disputed, and there were implications from that. Darwin, himself, without benefit of Mendel, was somewhat fuzzy and uncommitted in his notions of precisely how selected traits were passed on, even though he was confident in the outlines of his theory. Only in the 1920s to the 1940s was synthesis worked out that joined modern genetics to Darwin’s theory, wrapping it all up in a rigorous bundle.

Along the way, there were those moths. They seemed to clinch Darwin’s case because as the air around England, especially Manchester, grew black with smoke, the trees too were blackened under a pall of soot. Of course, the mutant black variety of the moth would be less visible to predators and would tend to squeeze out the white moth in the local populations. That’s exactly what was observed – the populations did change. It fit nicely with Darwin’s theory, but it turns out that the science behind the field observations was not so reliable. In fact, it may have been downright wrong.

Judith Hooper has narrated this story in her book, Of Moths and Men: An Evolutionary Tale. I happen to think she’s a rather good writer and that she does a very good job at explaining the details of how Darwinian Theory was given a firm quantitative and experimental basis with genetics. Yes, she’s a journalist, and she wants to tell a good story, so she emphasizes personalities a lot, but that stuff is part of the day to day mess of scientific advancement. Scientists are people like anyone else: it’s just that they all subscribe to a culture that provides some ruthlessly objective methods for winnowing fact from fiction. It can take a while, however.

I find it very interesting that this book is cited by creationists as “evidence” for the stupidity of Darwinian Theory. Does the fact that one piece of evidence may be wrong mean the entire Darwinian theoretical structure is wrong? Does it matter that this example was highly publicized and included uncritically in inumerable textbooks? Is this an evidence for a conspiracy? I think it just shows two things: science is hard; most people don’t bother too much about scientific details – especially textbook publishers. (This fact was discussed a year or so ago in the context of scientific “cliches” about basic physics.) After all, the principals in the controversy were all scientists, all evolutionists, mostly Darwinians, and none was a creationist or proponent of “Intelligent Design,” yet these know-nothings will trumpet this controversy as proof that Darwin is a fraud. (See Icons of Evolution.) The simple fact is, as one blogger put it, these people use their religion to “correct” science.

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2 Responses to Moths & Men

  1. Ed Darrell says:

    Read the book. Hooper is quite clear that Darwin was not wrong, nor was Kettlewell wrong. Hooper spends a couple of pages pointing out that nothing in the book supports creationism or intelligent design, and she says anyone who claims it does support creationism is a charlatan.

    Of course, that doesn’t slow the charlatans at the Discovery Institute.

    Also, you should make note that Michael Majerus reported last year on a seven-year experiment that confirmed Kettlewell’s original findings, though this latter test was much more rigorously set up than Kettlewell’s.

    See here:
    http://timpanogos.wordpress.com/2007/08/29/creationists-lose-key-texas-case/
    and here:
    http://timpanogos.wordpress.com/2007/08/29/majeruss-peppered-moth-powerpoint/

  2. lichanos says:

    Ed:

    I did read the book, as should be clear to anyone who read my post. You seem to be implying that I feel the creationists have a point – far from it! Do you think my post is unclear on this point??

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