Gradualism in Evolution (was Categories ...) (Agnosticism)

by George Jelliss , Crewe, Thursday, July 22, 2010, 00:24 (5238 days ago) @ dhw

Ernst Mayr wrote: "Individuals in a single population may differ by visibly different characters" (he cites eye colour and number of molars). -dhw, who is a great expert on these things assures us: "I don't think this has any bearing on the way complex organs arise out of mutations or adaptations."-So there. That's telling him! -Of course it has a bearing. It's by such minor changes that more major changes come about; for instance one can easily visualise teeth gradually developing into sharper points allowing for a change to a different diet, or what about the famous beaks of the finches.-dhw further expounds: "... the point at issue, ... is that a successful mutation will already entail complexity ... it will involve an innovation which works, i.e. a jump, not a gradual development."-Doesn't a slightly differently shaped beak more suited to opening certain nuts, say, constitute a successful mutation? This doesn't seem to involve any increase in complexity at all. dhw seems to have already decided in advance that any change however small is a "jump" and that jumps are impossible.-dhw gives the example: "A light-sensitive nerve is a jump from a nerve which is not light-sensitive (and where did nerves come from in the first place?)."-But why should any of the steps in this process be big jumps in complexity? A nerve is simply a piece of tissue that transmits a message in some form along its length. In a simple form it could just conduct heat, when its outer end touches a hot object. It would also be heated up when infrared rays impinged on it (heat being simply vibration of the molecules). A slightly greater sensitivity and it could detect red light rays.-dhw: "one might also question why a phenotypic mutation should take place if the original gene is already well suited to its environment." -This appears to assume that it takes place instantaneously, as opposed to being a gradual process. On the other hand there may be a rapid change in the environment that brings it on, out of the variation within the population; i.e. the individuals with the modification are better able to survive and propagate.-dhw admits: "Well, OK, maybe a small mutation is only a small jump, but a big mutation will be a big jump."-Yes and big mutations are usually unsuccessful mutations.-Erns Mayr wrote: "Darwinian gradualism is due to the gradual restructuring of populations."-dhw however ia a greater authority: "No it isn't."-That's telling him!-dhw: "The gradualism so vital to Darwin is the formation of complex organs through mutation and adaptation. ... it does not seem reasonable to me to assert that mutations and adaptations are initially NOT complex, and that such innovations can only come about gradually."-Well, this is absolutely denying Darwin's entire thesis!-dhw: "If an innovation is not successful, it will not survive."-Why not? If it is only a slight change, like a sharper tooth or a differently shaped beak it need make no difference, it will just add to the variation within the population.-dhw: "This does not in any way undermine the theory of evolution, and so I remain as mystified as ever by Darwin's insistence."-On the contrary, as dhw's original quote from Darwin himself says, dhw's insistence that evolution can only occur in big jumps entirely goes against Darwin's thesis.

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GPJ