Evolution (Evolution)

by dhw, Monday, March 31, 2008, 11:17 (5869 days ago) @ David Turell

David Turell "thoroughly disagrees" with my statement that natural selection does not depend on chance. Whitecraw agrees with me. - In fact, I don't think there is any real disagreement at all between us, but simply a problem of how far back we go in the chain of events. In my response to Kyuuketsuki I divided evolution into two factors: random mutation (chance) and natural selection (not chance). I take natural selection to mean the survival of those organisms best suited to cope with their environment. I took the third factor ... the environment ... for granted, but perhaps I should have added that the environment may also change by chance. Of course the three factors are interdependent, so David is right, but natural selection only comes into operation once the chance factors are in place, and then it works logically and not randomly, so whitecraw and I are also right. - David mentions the extinction of the dinosaurs and the trilobites. It is widely assumed that the dinosaurs (along with countless other species) were wiped out by a meteor. That was "bad luck" as David says, but in terms of our three evolutionary factors, it meant that dinosaurs were no longer suited to cope with their environment. Whether trilobites died out because of a meteor, climate change, an increase in predators etc. we don't know, but the same process applies: chance changes are followed by non-chance consequences. The current worry over the health of bees may serve as an illustration. The disease may have struck by chance, but the consequences will not be random: those plants dependent on bees will die out, insects dependent on those plants will die out, and everything else along the food chain will be in trouble. Let's hope it won't happen.