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Re: More on the genus problem

On Fri, Sep 18, 2009 at 3:59 PM,  <GSP1954@aol.com> wrote:
> The idea that the genus problem can be solved by defining genera in a
> simple phylogenetic manner as the last node before two sister species is
> defective. Assume that ungulates were extinct and known only from two complete
> skeletons, a giraffe and a bison. On the cladogram they form their own two
> species clade, and should then be the same genus. Obviously this is absurd 
> even if
> we accept multispecies genera, but why? Because of a piece of reality that
> sends cladistics screaming in terror....

Genus is an arbitrary way to classify things. All living being is a
result of a continuous changing (even if we consider the punctuation)
in a continuous chain (each living being havig their own path that
connect with the path of other living being at some point in the

So let star with the solitary giraffes and bisons - well they are very
different so we classify then in different genera. Obviously the
giraffes was born from another giraffe, so we will not classify then
in different genera, neither different species. Giraffe mother was
born from another giraffe mother... At the same time bisons has their
own parents, grand-parents, grand-grand parents... But at some time
their great-great-really-great parents were the same - were they
giraffe or bison? Probably neither giraffe nor bison, probably we
would classify them in a totally different genera from both. But
wait... so, giraffes and bisons 'changed' genus at some point. Which
point? Since no living being will bear another living being from a
different species, even less from a different genus (even at
punctuated equilibrium assumption) what was going on?

Let consider only the giraffe lineage:

It is conceivable that A and B are from the same genus, the same to C
and D. At same time A and D are from different genus. So, B and C are
from different genus? Not necessarily. And there is no paradox here.
We now about extant ring species. It is the same thing, but in
temporal dimension. Genus are not mathematically strictly transitive
thing, actually it is an arbitrary way to classify things - as much as

Yes, usefull, but arbitrary. And we classify things in a same or in
different genera as much as it was usefull.


Roberto Takata