Hybrids and genera
MexicoDoug at aol.com
MexicoDoug at aol.com
Fri Nov 8 02:09:36 EST 2002
Very Elegant & impressive points and counterpoints, Chris & Andy, Jeff and
Your well supported viewpoints have kindly supported my feelings that the
definitions of the species, genus, and on up system just philosophy no
different from "I think, therefore I am."
If we chose to define perfectly, we get equality. All based on circular
reasoning. After all, we are just using language to define language and
nature is above that. "SPECIES" is simply a word. You cannot "observe" a
"species". Only an individual. So if we choose to define in terms of
characteristics any of these "lineages" (another definition which is a
vicious circle in language). If you force a definition to fit, a lineage is
perfect. (perfect being an absolute) If you don't massage your definitions
carefully, you don't arrive at a perfect concept.
Humans are pretty conceptual, and the ability and imagination to
conceptualize has led to developments of catastrophic dimensions for our
species. But generalizations are not part of nature, nature proceeds by
individual events, 1-on-1, for example. Just as shorthand is good for a some
secretarial applications and not for others, and there is no absolutely
Just a little question for you guys. The "able to interbreed" criterion of a
species identity is a statistical, and not an absolute concept. If we don't
deal with the macro, populations you are loosely refering to (not a perfect
definition) implicit in "lineage". So, on the micro level, it is very easy
to find "incompatible" people among us who generally cannot produce viable
offspring for many reasons (enzyme/hormone distribution, pH, etc.), who when
paired with different people each can. Gives new meaning to some folks being
of a different species, doesn't it? Now bearing with me, if you ask the
practical question, "Is individual so-and-so of the same species as that one
(given we can only check individuals for breeding viability, so lineage is
then always an imperfect definition based on statistics.) Thus you will find
many 'species' within the human species by this interbreeding criterion, one
of the most celebrated of all criteria. So A individual produces viable
offspring with B individual. And B individual does with C individual. And C
individual does with D individual. But A doesn't with C, but A does with D.
An eloquent philosopher (the Spanish Antonio Machado) once said:
Caminante, son tus huellas (Wanderer, your footprints make)
el camino, y nada más; (the pathway, and that is all;)
caminante, no hay camino, (Wanderer, no pathway exists,)
se hace camino al andar, (Way is made upon wandering)
Al andar se hace el camino, (On wandering, the pathway is made,)
y al volver la vista atrás (and upon turning one's eyes behind)
se ve la senda que nunca (the footpath is seen that never)
se ha de volver a pisar. (has to be stepped upon again)
Caminante, no hay camino, (Wanderer, there is no pathway)
sino estelas en el mar. (But rather a wake on the sea.)
(A nice philosophical answer to a philosophical question...) And I would
venture that taxonomy is a relative science, unlike perhaps number theory,
and thus taxonomy will continue to stive into infinity getting more and more
useful generalizations, and that since different generalizations may be more
beneficial depending on the application, different taxonomies will forever
continue to coexist in a democratic world.
stelenesR at EpMoObVoEx.com
En un mensaje con fecha 11/07/2002 11:48:47 PM Central Standard Time,
drdn at mail.utexas.edu escribe:
> At 11:50 AM 11/7/2002 -0800, you wrote:
> >Howdy Lepers,
> >Let's also not forget that the ability to interbreed is a symplesiomorphy
> >- a shared
> >primitive feature, that is not relevant to the empirical discovery of
> >species and
> >other taxa.
> Yes the inability to interbreed may certainly be a recently acquired
> character that prevents closely related species from interbreeding, but it
> also may be due to gross physiological incompatibility accumulated over a
> long time in lineages that have not recently interbred.
> >Also, taxonomy could never fully "reflect phylogeny," because if we had
> >access to the
> >complete history of phylogeny, there would be only one taxon ("life"),
> >with a bunch
> >of polymorphic features that have changed in frequency over time.
> I disagree. In the fossil record I see clear evidence of punctuated
> equilibria as the norm. Our taxonomy at the species level is labelling
> these equilibria.
> >The very process
> >of conceptualizing more or less inclusive groups of organisms as species,
> >etc. imposes discrete boundaries among the entities identified, while the
> >process of
> >lineage splitting has no single ontological point at which the lineages
> >divided. Kind of like, when do the Rio Negro and the Rio Solimo~es become
> >the Amazon
> >- at the point when the waters first meet, or the point where they are
> >mixed (two very separate places)? Are they one river, or three? A
> >taxonomist would
> >say three, a lineage-minded person would say one.
> Sorry. I would have to run the rivers upstream to find an analogy with the
> tree of life.
> >Taxonomy is not intended to provide an accurate map of the evolutionary
> >process, and
> >its logical and empirical basis is at odds with the notion that taxa blend
> >into one
> >another. Rather, it is an epistemological artifice that treats groups of
> >that are hypothesized to represent parts of lineages as though they were
> >things with fixed character states in order to make powerful predictive
> >about relationships among them.
> I really disagree with this at the species level.
> > Sort of a calculus of biodiversity.
> >Last, I disagree with the implication that there is an "objective
> >definition" of species. Given that there are multiple, competing
> >definitions in the
> >current literature, it is quite clear that the definition of species is a
> >rather than an empirical or logical problem.
> No. I think that there are several valid species concepts each of which may
> operate under local conditions. A linear gradualist could not be concerned
> with species concepts as there would be no switch from one species to the
> next. A punctual systematist on the other hand will place the species
> boundary at the punctuation. Unfortunately punctual systematists are too
> often perceived as racists and that is not politically correct.
> Unfortunately I see the possibility of more than science at work here.
> > From my perspective, species are really
> >no different than genera or families, which also "can be thought of as
> >(more inclusive ones), if one desires to do so, after they have been
> >recognized on
> >the basis of fixed character state differences. Others probably have a
> Yes. I am not ready to accept neatly punctuated genera. I think they are
> more the statistical refuse of irregular extinction. I do not think the
> problem is semantic but one of familiarity with the fossil record, versus
> neo-Darwinian theory that insists on gradual and constant change rather
> than the stability of fine tuned selective interaction with a finite
> complex habitat..
> ..................Chris Durden
> > That's the great thing about semantic problems.
> >- Andy Brower, Oregon State U.
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