Evolution (Introduction)

by George Jelliss , Crewe, Sunday, July 19, 2009, 16:33 (5605 days ago) @ David Turell

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 m ore 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. - 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? - 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. - So it seems to me that this distinction you are making between macro- and micro-evolution is a chimera. It is just where we choose to draw the line. How many hairs must a man lose before we call him bald?

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GPJ