Categories or Degrees of Existence (Agnosticism)

by David Turell , Thursday, August 05, 2010, 14:46 (5223 days ago) @ dhw


> David asks, in the light of the new discovery and its relation to the Cambrian Explosion, "Where is Darwin's gradualism?" This is a point of the theory that I have never quite understood. Darwin is unequivocal about its importance: "If it could be demonstrated that any complex organ existed which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down." (Origin, p. 214) In some respects he is on safe ground, because no-one can ever prove that there were no transitional forms, just as no-one can ever prove that there is no God. The Eldredge-Gould concept of 'punctuated equilibrium', however, contradicts that of 'Natura non facit saltum' and it certainly seems to be more in keeping with the fossil record as we know it. What I don't understand is why gradualism should be so crucial to the theory as a whole. It therefore seems to me that evolution doesn't depend on gradualism at all. Perhaps someone can enlighten me.-
Eldridge-Gould disturb(ed)some old school rigid Darwinists. In the past I've mentioned Reznick's guppies, now studied 20 years. They can change size to avoid preditors in a two-year period. Now we find that sticklebacks can adapt to colder waters in a three-year period. Epigenetic change may drive evolution more importantly than 'gradual' Darwinian suppositions. -
http://www.publicaffairs.ubc.ca/2010/08/04/mr-10-111/