>Thinking a little (perhaps VERY little), there are several reasons why I
>am skeptical that macroevolution is "microevolution writ large."
>3. The fact that animals appear in very definite classes, cats, dogs,
>elephants, etc. Yes, I know the "niche" arguments, but they are not
>really very satisfying.
I will make a brief reply to the above comment. Thge fact is, the
boundaries between taxonomic groups are NOT clearly drawn. When you move
back in time toward the time of appearance of a new taxonomic group,
distinctions become less and less clear. It is a very common occurrence in
paleontology that there is considerable uncertainty and disagreement among
workers regarding the proper classification of early appearing forms. The
morphologic features that define recognized living groups do not appear in
the fossil record simultaneously. Thus some fossil forms bear some but not
all defining characters of a living group, and some bear the defining
characters of more than one distinct taxonomic group.
This pattern characterizes the appearance of many class level groups --
mammals, birds, reptiles (amniotes), amphibians (tetrapods), bivalves,
gastropods, scaphopods, rostroconchs, etc.
Keith B. Miller
Department of Geology
Kansas State University
Manhattan, KS 66506
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