ideacenter.org/contentmgr/showdetails.php/id/1490 [....] Implications of Genetic Convergent Evolution for Common Descent The aforemtnioned paper in Trends in Genetics, Causes and evolutionary significance of genetic convergence, notes that that genetic convergence is not uncommon, even though only a restricted number of substitutions at the genetic level can create novel phenotypic traits. This data not only shows that functional genotypes are rare, but it also poses a much deeper problem for evolutionary thinking--one that challenges the very basis for constructing phylogenetic trees. The main assumption behind evolutionary trees is that functional genetic similarity implies inheritance from a common ancestor. But convergent genetic evolution shows that there are many instances where functional similarity is not the result of inheritance from a common ancestor. So when we find functional genetic similarity, are we to assume that it represents a homologous DNA sequence, or a convergently similarity sequence? This poses great difficulties for those who wish to build evolutionary trees under the assumption of common descent. I am hardly the first to recognize this. Evolutionary paleoecologist Simon Conway Morris--who is not an intelligent design (ID) proponent--quite explicitly observes that convergence poses a major difficulty for the construction of phylogenetic trees: I believe the topic of convergence is important for two main reasons. One is widely acknowledged, if as often subject to procrustean procedures of accommodation. It concerns phylogeny, with the obvious circularity of two questions: do we trust our phylogeny and thereby define convergence (which everyone does), or do we trust our characters to be convergent (for whatever reason) and define our phylogeny? As phylogeny depends on characters, the two questions are inseparable. ... Even so, no phylogeny is free of its convergences, and it is often the case that a biologist believes a phylogeny because in his or her view certain convergences would be too incredible to be true. ... During my time in the libraries I have been particularly struck by the adjectives that accompany descriptions of evolutionary convergence. Words like, remarkable, striking, extraordinary, or even astonishing and uncanny are common place...the frequency of adjectival surprise associated with descriptions of convergence suggests there is almost a feeling of unease in these similarities. Indeed, I strongly suspect that some of these biologists sense the ghost of teleology looking over their shoulders. (Simon Conway Morris, Lifes Solution: Inevitable Humans in a Lonely Universe, pp. 127-128 (Cambridge University Press, 2003).)
Posted on: Mon, 03 Feb 2014 09:46:35 +0000
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