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Edited on Sun Apr-19-09 11:38 AM by mike_c
I ask because you discuss evolution rationally, but in a way that few, if any, biologists would accept. For the record, I'm a working biologist and academic scientist, so I'm pretty familiar with that crowd's perspectives.
First, natural selection has NOTHING to do with "survival of the fittest" unless we're talking about population genetics, i.e. multigenerational "survival" (= persistence) of adaptive alleles. In other words, differential reproductive success, with better adapted individuals producing, on average, more offspring than less well adapted individuals. Survival is only necessary for offspring production. Most organisms senesce-- survival beyond the peak reproductive portions of their life histories is irrelevant to fitness.
Second, you're mistaken to conclude that "fitness" is an ill defined concept. From an organismal standpoint, it is defined as the production of viable offspring. It is better expressed as "reproductive fitness," which we often shorten to simply "fitness" for the sake of convenience, but which non-biologists often misinterpret. From a genetic standpoint, it is the persistence and relative proportional growth or decline of specific alleles in populations over time. Alleles that foster reproductive success are "fit." Deleterious alleles are less so.
Third, your contention that natural selection cannot contribute to speciation is not supported by anyone I know. Speciation is something of a red herring among creationists and other detractors of evolution. There are several problems, not the least of which is that the notion of "species" is arbitrary, at best. No successful, universal definition of the term "species" exists at present-- it's a term of convenience, nothing more. Also, natural selection is only one of several mechanisms for speciation. Finally, speciation itself is not a homogeneous process- there are several types, likely with at least partly differing mechanisms.
In truth, the genomes of all organisms living on Earth are continuous elaborations in form and function, but sometimes with observable discontinuities that allow us to distinguish consistent differences separating different "types" or taxa. Think of them as genomic clusters in the universe of all possible shared genomic traits for all organisms living on Earth. What we call a "species" is simply a genomic cluster distinguished sufficiently from its neighbors-- related taxa-- to exhibit observable differences in phenotype, reproductive isolation, etc. Sometimes just spatial or temporal location.
When you consider the genetic continuity of all life on Earth, it's easy to see how natural selection plays a role in speciation. ANY process that fosters the accumulation of genetic differences between related organisms-- that fosters clustering in the universe of possible shared genomic states-- contributes to speciation, including natural selection.
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