Evolution (Introduction)

by David Turell , Sunday, July 19, 2009, 21:56 (5401 days ago) @ George Jelliss
edited by unknown, Sunday, July 19, 2009, 22:41

DT wrote: I think Matt is closer to understanding my pattern of theorizing than George is.
> 
> I had written: I still don't quite understand your distinction between micro- and macro- evolution.
 
> and I still don't!
 
> DT: Microevolution is variations in species adapting to changes in environment, etc. These are small and the species can still be identified as the same species. Macroevolution is the appearance of new species from the old ones, a definite step forward in the more complex direction that evolution has followed. - 
 
> It seems to me then that deciding where to draw the line to say that a given species has evolved into a new species is somewhat arbitrary, since every step is very slight but the overall result is noticeable. - You are hung up on Darwin's proposal that tiny steps make new species. I have noted on several occasions that there are also giant jumps in the tree to the new species from the old.
 
> Ernst Mayr in "What Evolution Is" mentions "ring species" where a chain of populations curves round an obstacle, a mountain or desert say, and overlap at the ends of the chain where they do not interbreed. Where in the chain does the species become a new one? - Loss of interbreeding is the standard dividing point, but I've shown that is arbitrary and is imperfect. I am hopeful as we follow biochemical marker molecules, we may have a better dividing line. 
 
> Similarlty in the evolution of the whale, gradual changes lead from pachicetus to rhodocetus to dorodon (the fossil species mentioned in the RD video). Since these species have never coexisted at the same time the test of whether they could interbreed does not decide the issue of whether they are distinct species, but there are sufficiently distinct features to justify calling them separate species, but all part of the whale's family of ancestors. - I agree with your analysis of the whale tree, but look at where those nostrils are. It would take major plastic surgery to make those moves in the skulls. Those are the big jumps I mean; big jumps separated by many years. For Darwin's theory's sake where are the tiny nostril adjustments as they move up the skull? Are you implying that those intermediate fossils are still missing? We don't know that so I am proposing that the jumps may be real. - > So it seems to me that this distinction you are making between macro- and micro-evolution is a chimera. - No George, you are wrong. This is not an imaginary difference. Again, why did Gould and Eldridge invent 'punctuated equilibrium'? Because of big jumps. It is not just that fossils are missing; there are things like the Cambrian Explosion to explain. Prior layers of the Earth reveal sponges and Bilaterians, not animals with appendages and several organ systems. Since the Burgess Shale discoveries about 1880-90, no intermediates worthy of the name have been found. The layers of the Earth are not missing for those Geologic periods. Bad luck or no fossils? We don't know and either possibility still exists.