Definitions (Evolution)

by dhw, Tuesday, April 08, 2008, 18:47 (5860 days ago) @ David Turell

David Turell has referred to my statement that there is sufficient evidence for me to believe in natural selection. He agrees that this works on the level of adaptation to the environment, but not on the level of one species turning into another, and he asks if I think natural selection created the 'tree of life' "illustrating common descent". - I had the impression that you and I were in agreement on this problem, but maybe not, so let me try to break my own beliefs down into their constituent parts. I can well believe that life began with simple forms (possibly bacteria). If this is so, then obviously it follows that more complex forms evolved from them. I accept the theory of natural selection when it = the survival of those organisms best able to cope with their environment. As you say, organisms adapt, and those features that are advantageous will be passed on. My problem, second in line to the origin of life itself and reiterated many times on this website, is mutations. These can only take place in individual organisms, or maybe a group of organisms within the same environment. Every "advance" from bacterium to human (advance in the sense of additional complexity, not necessarily of efficiency ... see whitecraw) will have been produced by mutations: totally new concepts and mechanisms such as vision, hearing, smell, limbs, sexual reproduction, consciousness etc., with all the necessary links through an evolved nervous system to an evolved brain. - It's a point we keep coming back to: the difficulty of believing that original forms and systems could emerge by chance from nowhere. Although the alternative of design raises huge problems of its own, that does not make the chance theory any easier to believe. So we are left with a massive question mark: if the starting point is bacteria and we take humans as a point of comparison, and if we accept that evolution (= mutations plus natural selection) led from one to the other, over no matter how many billions of years, what is the source of the inventive power to produce each of the innovations? The alternative answers as I see them are: 1) the original forms of life and all the subsequent mutations were random acts caused by chemical reactions and environmental factors; 2) the original forms of life were programmed with the potential for all the subsequent changes; 3) the subsequent changes were manipulated by an outside intelligence. You have asked: "Did natural selection create the tree"? Not according to my understanding. The tree may have been created by mutations, each of which was then subject to natural selection, but the mechanism driving the sheer creativity of these mutations is far beyond my comprehension.