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Re: Ancestors... (was Re: Stratigraphy, biogeography & cladograms)



George wrote [about species]:
>It is not a "human" construct, it is a contingent construct: a species is the
>cross-section of a lineage at a particular time. All the extant species that
>we see around us today are the cross-sections of lineages (by the "present")
>that go back in time to the first life forms (and extend into the indefinite
>future to life forms as yet unevolved). Likewise, fossils represent species
>that are the cross-sections of lineages at earlier times. A definition of
>species that doesn't incorporate time is headed for trouble.
        I agree wholeheartedly. Indeed, if this is all anyone means by
"lineages", I can support it fully. I grow concerned however, in that my
understanding was that the term is used mostly in association with the
process (common in invertebrate paleontology and older vert paleo) of
arranging taxa stratigraphically and then drawing lines of ancestry and
descent between them, with the result that one gets pretty branching
diagrams with few speciation events and a low, steady rate of evolutionary
change.
        Wagner

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     Jonathan R. Wagner, Dept. of Geosciences, TTU, Lubbock, TX 79409-1053
 "Only those whose life is short can truly believe that love is forever"-Lorien