by Dave Person
February 02, 2005
No biological or life scientists debate the existence of evolution. It would be like debating the existence of the sun or moon. Scientists, however, debate how it occurs. Two major theories compete as explanations, natural selection and neutral evolution. Natural selection is what Charles Darwin's great work "Origin of Species by Means of Natural Selection" is all about. Darwin didn't invent evolution, the phenomenon is as ancient as life, but in 1859 he described a plausible mechanism by which it occurs. Alfred Russell Wallace, a scientist working independently of Darwin published a similar theory of natural selection at the same time. Basically natural selection is "survival of the fittest". Individuals in a population that are better adapted to their environment tend to survive and reproduce more successfully than less well suited individuals and pass on their qualities to the next generation. All dogs evolved from wolves, we were just the agents of that evolution! That we were able to eventually breed Pekinese dogs from wolf-like ancestors attests to the overwhelming (and non random) power of natural selection. The theory of neutral evolution argues that the main force driving evolution is change in gene frequencies due to mutations and the shuffling of populations by forces independent of natural selection. Both theories coincide nicely because genetic mutations create the raw material on which natural selection can act. The scientific debates generally focus on whether a neutral process or selection, is the most powerful engine driving evolution.
Evolution is not a theory, it is a fact. Natural selection and neutral evolution are theories explaining how it works. They are not beliefs or religions because they spawn hypotheses and reliable predictions that are testable with real data. They have held up very well after many years of scientific scrutiny. Finally, evolution is not a theory of the origin of life but it is absolutely a fact of life for all species, including humans.
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