>What I was thinking about at the time, and did not express it, was a gedanken experiment. Suppose the world we inhabited were one in which any organism could (and often did) mate with any other. Then dog-cats, and elephant-tiger-apes, and etc. etc. beings would, if not abound, not be unthinkable, and the sheer variety of living beings, including human-snail combinations, to take one absurd example, would be effectively infinite. Now put yourself in such a (terrifying) world and ask if the variety of living organisms must not be excellent evidence of
"microevolution writ large?" In such a world, the answer would surely be "yes," and, indeed, overwhelming.<
>But we do not (thankfully) inhabit such an imaginary world, and, therefore, I was thinking that the argument must therefore be at least somewhat weaker here.<
Actually, such a world would suggest the existence of some sort of macroevolutionary factors distinct from microevolution (defining microevolution as the everyday infraspecific variation, e.g. children not identical to parents). Some species-level effect would have to be acting to counter the tendency for every organism to become a generic mix of every species. A significant barrier to interbreeding seems to be necessary for evolution to produce different kinds.
The reason that we do not immediately recognize numerous transitional forms, nascent organs, and the like in present-day organisms is that we do not know what will happen in the future. If an organism is evolving into something else, we do not know until it gets there.
Dr. David Campbell
Old Seashells
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bivalve@mail.davidson.alumlink.com
That is Uncle Joe, taken in the masonic regalia of a Grand Exalted Periwinkle of the Mystic Order of Whelks-P.G. Wodehouse, Romance at Droigate Spa
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