cladism's greatest weakness

Tom DiBenedetto tdib at UMICH.EDU
Tue Sep 21 11:55:58 CDT 1999

Richard Zander wrote:

>This is yet another example of the forever-ongoing battle of realists (who
>assume that the world is observer-independent and knowledge is objective and
>absolute), and pragmatists (who ignore the question of observer-independence
>and act in ways that maximize the usefulness of information, no matter how
>such information is generated).

Although I agree that realists assume that the world is
observer-independent , I do not think that the notion of knowledge
being objective and absolute is part of the realist perspective. I
consider myself a realist; I assume that there is an objective reality
which I attempt to describe, but I also understand that knowledge is
always approximative of that reality, and inherently subjective. To me
the enterprise of science entails a constant effort to transcend our
personal subjectivity, by arguing, discussing, and experimenting within
a rational framework, to arrive at a consensus of educated opinion
which is, of course, still subjective, but is an agreed-upon
subjectivity, encompassing many people. In this way we hope to
asymptote toward the unreachable goal of objective knowledge (rather
like the way in which we try to measure the area under a curve (the
real world = the curve) using ever-finer rectangles made up of straight
lines (straight lines=our ideas).
I dont know of any realists who assume that knowledge is ever absolute,
or objective. Only religous types seems to do that.

>Species at least exist as tools, and are useful even though their
>circumscriptions are labile over time as new information presents itself.
>Clades at least exist as tools.

Clades seem to me to be, at the same time, an empirical finding of
comparative biology, and a necessary deduction from the theory of
evolution. To the extent that we can ever attribute confidence to our
empirical discoveries, and to the extent that we accept the evolution
of life as a fact, then clades seem to me to be real, to a similar
extent that we consider electrons, or the orbit of the earth to be

>No, ancestral species do not have to
>disappear (it is not a convention), but given the data sets, we seldom find
>a sister branch (as a computational tool, mind you) with no syn- or
>autapomorphies (so practically speaking ancestors disappear even if the
>speciation event that destroys them is just gradual change).

This discussion is totally bound up in the subtlties of what you
consider a species to be. I dont know of any cladists who accept
Hennigs notion about ancestral species going extinct. Speaking just for
my self, it has always seemed pretty clear to me that when a
species-level taxon diverges (whether through "budding" or an even
division), the taxon (the lineage) becomes a higher taxon (becomes a
diverged, i.e. a more complex lineage). If we sent a colony off to
Mars, and they became reproductivly isolated, then the taxon Homo
sapiens would no longer be a species level taxon, it would refer to a
more complex lineage, and would be a higher taxon. Nothing has "gone
extinct" or disappeared.

>Concepts are real. Let's agree on the minimum reality that "things out
>there" are at least valuable conceptual tools.

I dont understand this at all. The "things out there" are not
conceptual tools, they are the reality.  We develop conceptual tools to
describe and deal with the "things out there".

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