Natural Selection: Domains, Levels, and Challenges

By George C. Williams | Go to book overview
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Appendix: Excerpts from some classic works on adaptation

I believe that the following excerpts from works by Galen ( May, 1968) and by William Paley ( 1836) are worth close attention by all biologists. Both illustrate how adaptation can be explored by seeking conformities to a priori design specifications. Galen's and Paley's main arguments are thoroughly mechanistic, and their occasional errors arise from the primitive state of physical science in their times, and from their total ignorance of natural selection and historicity. Thus Paley could show that the lens contributes to vision by focusing a sharp image on the retina, but he had no scientific understanding of what vision was designed to accomplish, and no way of knowing that some features of the eye might be nonadaptive historical legacies.

I hope that these excerpts will induce many readers to read the whole books. Many other historically significant works might also be read with profit by modern biologists. Galen and Paley built heavily on the works of Aristotle, now widely available in translation. A more recent classic that everyone ought to read is H. J. Muller's Evidence of the Precision of Genetic Adaptation ( Muller, 1948). He used commonly studied mutations to establish that normal wild-type characters of Drosophila melanogasterare optimized. He did this by showing that the mutant forms, even those with seemingly trivial effects on the number and shape and distribution of bristles and wing veinlets, are functionally impaired by these departures from their optima. His main focus was an exploration of the elaborate machinery of dosage compensation whereby both females, with two X-chromosomes, and males, with one, normally develop almost exactly the same phenotypes for characters affected by genes on that chromosome.

Muller's essay is of 65 pages, far too long to include as part of this appendix, and I was unable to extract any small part that would capture the flavor of the whole tightly reasoned argument. It has a surprisingly modern ring after 44 years. While reading it I find it hard to bear in


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Natural Selection: Domains, Levels, and Challenges


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