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Re: going offlist on Protista, bacteria
<Birds are not superior to dinosaurs, so why give them a "Class" of their
Easy: because they are obviously different.
<Vertebrates are not superior to flatworms, any more than flatworms are
superior to sponges, or any metazoan
life form is superior to any bacterium.>
These are examples of obviously different groups whose difference you are
<Go way back to the base of the Aves, and the differences between birds and
dinosaurs resolves into one or two evolutionary innovations. There's
nothing so different between _Archaeopteryx_ and (say) _Sinornithosaurus_
that one deserves to be raised into a "higher" class than the other.>
Go far enough back in any group you choose to distinguish and the
differences from an ancestral group will be small, by definition. And,
because the whole list of differences between the two groups appear over
time, you also have to choose how many of those differences have to be
present to say that a specific animal is part of one group or the other.
The difference in approach being considered is: are you emphasizing the end
result (bird/dinosaur) or the beginning of the separation between the two
groups? Doesn't it seem most reasonable to emphasize the end result when
deciding when differences are large enough to distinguish a group?
Also, remember that when you do start from the end and work backwards, there
are offshoots not now extant, but you could (theoretically) trace a straight
line back to another group. The word 'progress' may be too connotative for
you when looking at this progression (heh heh), but you're certainly looking
at a movement through time to a given result.
Many people start with the easy observation (That's a bird.) and don't mind
the difficulty that some early ancestors are hard to analyze. I think that
this attitude should be acknowledged, even when disagreed with, and not
criticized as the result of a presumption.
End assertive moment.