Non-Darwinian evolution and the bread of life : genetic drift, repetitive DNA, philosophy of science
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This paper explores what would happen to a chromosomal segment that evolves randomly, without the surveillance of natural selection. In these circumstances a single segment present in some individual organism at any given starting time will eventually spread through the population until it becomes fixed in the entire gene-pool - or more properly the "segment pool". At the same time, the continual deletion, duplication and insertion of nucleotides in a randomly-evolving segment of DNA will lead to fixation of individual nucleotides in the total pool of nucleotides in all the homologous segments in the species. When this genetic drift at the nucleotide level is examined in detail, it is seen to provide a simple, natural solution to a contemporary problem in molecular evolution: the prevalence of apparently functionless segments consisting of simple nucleotide sequences repeated tandemly thousands to millions of times. The solution exemplifies a class of scientific theories that are difficult or impossible to corroborate experimentally, even though they may be intellectually satisfying and of considerable practical importance in the progress of science.