Artificial Selection

By Branden Holmes (Surroundx) on November 28, 2010

Charles Darwin preferred not to gather his information from theoreticians, but rather from people who had practical experience in their area of expertise. In the first chapter of Origin, “Variation Under Domestication”, Darwin sought to show a number of things. The most important of these was that: “Our oldest cultivated plants, such as wheat, still yield new varieties: our oldest domesticated animals are still capable of rapid improvement” (pg. 25). If that was not found to be the case, if variation had been shown to stop after artificial selection after only a few generations, it could never have continued for the millions of years that nature requires for such diversity as we see to have come from one or a few ancestors. That is probably the greatest hurdle to evolution, which Darwin showed to be fallacious all those years ago.

The main purpose of the first chapter was, however, to detail the extraordinary amount of change that has occurred in the different domestic breeds which were derived from a single, or few, wild species. He took a particularly strong interest in pigeons, “Believing that it is always best to study some special group, I have, after deliberation, taken up domestic pigeons. I have kept every breed which I could purchase or obtain, and have been most kindly favoured with skins from several quarters of the world...I have associated with several eminent fanciers, and have been permitted to join two of the London Pigeon Clubs.” (Origin, pg. 39) Darwin’s subject was well chosen as domestic pigeons exhibit much diversity between all of the different breeds: “Altogether at least a score of pigeons might be chosen, which, if shown to an ornithologist, and he were told that they were wild birds, would certainly be ranked by him as well-defined species. Moreover, I do not believe that any ornithologist would in this case place the English carrier, the short-faced tumbler, the runt, the barb, pouter, and fantail in the same genus;...” (Origin, pg. 41) Yet he was convinced, based upon his enquiries, that they were all descended from a single wild species: “Great as are the differences between the breeds of the pigeon, I am fully convinced that the common opinion of naturalists is correct, namely, that all are descended from the rock-pigeon (Columba livia)...” (Origin, pg. 42) Darwin saw the potential change that could occur in such a short period of time as even a few thousand years, which, by nature’s standard is a fleeting second, hardly discernable. And although nature does not change species anywhere near as fast as farmers do, given the immense periods of geological time at her disposal, great changes in nature are inevitable: “It is not to be supposed that species in a state of nature ever change so quickly as domestic animals under the guidance of methodical selection. The comparison would be in every way fairer with the effects which follow from unconscious selection, that is the preservation of the most useful or beautiful animals, with no intentions of modifying the breed; but by this process of unconscious selection, various breeds have been sensibly changed in the course of two or three centuries.” (Origin, pg. 413-4) But because Darwin lived before the discovery of DNA, and was sadly unaware of the almost contemporaneous Mendelian revolution, his theories have had to be augmented to take into account these discoveries. He had to use the analogy to artificial selection because he didn’t know the origin of variation: mutations. The analogy to artificial selection is nowadays unnecessary, but with his lack of documented cases of natural selection, he needed a model that people could understand. Because Origin was written for the British public, after all. But in what he did theorize about he was remarkably prescient and many of his views are still remarkably modern 129 years after his death. His many experiments on germination of seeds soaked in saltwater to find out whether colonization of distant lands was possible, were ingenious. The fact that his theory has been modified is only to be expected given the fact that science has moved forward immensely in the past 151 years (since Origin was published, but he was relying on data from 20 years prior when writing it). He was only a single man, versus the many 1,000’s of scientists who have spent lifetimes researching specialized areas of evolution. In the 21st century, we can study natural selection directly. None of this should take away from the immensity of Darwin's discoveries.

Related articles:
artificial selection, Evolution

About Branden Holmes
I am an amateur evolutionist interested in the theoretical side of the subject.

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