Wonderfully well-written,
Of Moths and Men by Judith Hooper is the tale of Bernard Kettlewell and the people who eventually caught up with him. His experiments on industrial melanism established the peppered moth as *the* textbook example of natural selection in the wild, but over time the deficiencies in his approach became gradually apparent.
Kettlewell's experiments were poorly designed and inconsistently executed, but now that the truth is out there are still many scientists, particularly in Kettlewell's home country of the British Isles, who nonetheless hold to the view that bird predation explains the differential success of the light and dark forms of the peppered moth. In other words, Kettlewell was right, even though his experiments turned out to be wrong.
This position is difficult to understand given that a generation of scientists have failed to confirm Kettlewell's experiments, and I find myself more aligned with those who believe that while environmental factors and natural selection are certainly the source of the color changes, the situation in nature is so complex as to defy analysis.
Like many insects, the peppered moth passes through four stages: egg, caterpillar, larvae and moth. The agent of selection could be acting at any one of these stages, with the color of the adult moth only a side effect. The involved gene could directly control color, or it could be a related gene, or it could be a gene that controls sensitivity to environmental factors. Or any number of other things. The important point here is that we don't know.
Experiments in the laboratory have established the principle of selection beyond all doubt, but we have not yet found clear demonstrations of natural selection in the wild. Given the huge number of interacting factors we may never be able to do so. For example, in the case of the peppered moth one scientist believes that you really need to follow a couple hundred individual moths and observe their resting place in the tree canopy of forests to see if bird predation is indeed significant. This simply isn't going to happen, if not because of the difficulties involved then because the world has moved on from studying organisms in their native environment to analyzing their genomes in the laboratory. It's all molecular now.
I'm a prime proponent of owning a large library of books that I haven't yet read, but having checked this one out of the library I plan to buy it anyway - it's that good, not just as science history but also as a reference work. The index is excellent. If I had a rating system this book would be at the top: 4 stars.
--Percy
[This message has been edited by Percipient, 12-30-2002]
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