Re: Strange thoughts on PN - was Re: BAD vs. BADD

[Martin Baeker <martin.baeker@tu-bs.de>]

> Giving arbitrary non-monophyletic groups names is heuristically damaging for
> the same reason that using Linnean ranks is a heuristically poor practice;
> naming them encourages people to think that the name or ranking is "real" in
> some ontologically valid sense. 

For pratical purposes, it is, I think, in many cases. That's what all
of this argument is about. Canidae are a rather clear-cut group
now-adays, as are primates, perissodactlys or whatever.

Perhaps it is just my insufficient knowledge of animals, but doesn't
it seem as if the majority of animals can easily be grouped by their
morphology? And isn't it somehow dangerous to claim that all this is
arbitrary and worthless if it is so easily observed? (See below for an
example.)

BTW, I think two different things are frequently confused here: One is this
type of "grouping-by-morphology" (lumping all dog-like mammals as
Canidae etc.), the other is assigning ranks to these groupings.
(Seems I was myself guilty of this in a previous post...)  For the
ranking then leads to trouble if one group splits much more than
others do (wasn't it once said that insect orders are more like
vertebrate classes?). 

> It may be "unwelcome" to some (maybe even
> most) people to have to use terms like "non-avian dinosaurs" or "non-human
> primate", but using them encourages us to be intellectually honest, by
> reminding ourselves that the group is arbitrary, and that we must be careful
> to ensure that the characters under discussion are actually restricted to the
> group at hand, not simply an illusory lumping of characters from animals we
> asssume are "alike" in some way.

Shouldn't there be a clear-cut systematic way to talk about the set
"bony fish" without Tetrapodes? Do you really say that this grouping
is worthless because we know of perhaps a handfull of fossils (from
probably more than 50000 fish species known all together) that would
be difficult to place? Isn't it intellectually even more misleading to
tell people: No there is no such thing as bony fish, unless you
include humans?

Cheers,

Martin. (Who still tries to form an opinion on all these things.)

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