orthogenesis

[Richard.Zander at MOBOT.ORG]

Opp. Rereading my post of a couple minutes ago, the last sentence implies
that Grehan is not a genuine biogeographer. He is. I'm not.

R.
______________________
Richard H. Zander
Bryology Group, Missouri Botanical Garden
PO Box 299, St. Louis, MO 63166-0299 USA
richard.zander at mobot.org <mailto:richard.zander at mobot.org>
Voice: 314-577-5180;  Fax: 314-577-9595
Websites
Bryophyte Volumes of Flora of North America:
http://www.mobot.org/plantscience/bfna/bfnamenu.htm
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Shipping address for UPS, etc.:
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4344 Shaw Blvd.
St. Louis, MO 63110 USA


-----Original Message-----
From: Richard.Zander at MOBOT.ORG [mailto:Richard.Zander at MOBOT.ORG]
Sent: Thursday, May 19, 2005 10:14 AM
To: TAXACOM at LISTSERV.NHM.KU.EDU
Subject: Re: [TAXACOM] orthogenesis


John Grehan asks fundamental, challenging questions. One must always posit
initially poorly supported hypotheses to explain something natural, and some
may appear quasi-essentialist until, surprise, some experimentalist detects
a mechanism. On the other hand, really simple explanations that explain
everything can border on the supernatural. And what is proof? or likelihood?

It may not be necessary to have one explanation of everything; physicists
(e.g. F. Dyson) are toying with the idea that a unified field theory may be
impossible and not necessary, given what we know of the universe.

For a theory to stand, however, it must have some point or pragmatic value.
I've inveighed at length here on Taxacom against the T. Aquinas-style logic
that once you've chosen the correct first principles, all deductions must be
correct. Presuppositionalists, also, first conceive that their assumptions
are correct and if they can come up with a coherent, well structured, really
neat theory, their assumptions must have been correct; contrary to this,
other first principles can also be used to come up with coherent, well
structured, really neat but different theories.

Do we have a coherent, well structured, really neat theory to compare with
J. Grehan's? Even if not terribly coherent, is our theory more predictive or
passes some test better than orthogenesis? What is the test? We do not have
to prove orthogenesis unreasonable, just find something better and more
valuable in practice.

For a nice review of a recent tome on historical biogeography, see the
recent Systematic Biology 54(2): 338-340. 2005. It touches on
panbiogeographic method, seems clearly thought out, and the writer is
apparently a genuine biogeographer.


______________________
Richard H. Zander
Bryology Group, Missouri Botanical Garden
PO Box 299, St. Louis, MO 63166-0299 USA
richard.zander at mobot.org <mailto:richard.zander at mobot.org>
Voice: 314-577-5180;  Fax: 314-577-9595
Websites
Bryophyte Volumes of Flora of North America:
http://www.mobot.org/plantscience/bfna/bfnamenu.htm
Res Botanica:
http://www.mobot.org/plantscience/resbot/index.htm
Shipping address for UPS, etc.:
Missouri Botanical Garden
4344 Shaw Blvd.
St. Louis, MO 63110 USA


-----Original Message-----
From: John Grehan [mailto:jgrehan at SCIENCEBUFF.ORG]
Sent: Thursday, May 19, 2005 8:39 AM
To: TAXACOM at LISTSERV.NHM.KU.EDU
Subject: [TAXACOM] orthogenesis


Steve Manning wrote:

> >7. Orthogenetic development (phylogenetic constraint by molecular
drive)
> >is of primary importance in evolution.
>
> Can you be more specific as to what this really means (relatively
> briefly)?  I have often thought that actually evolution is just one
> energy-driven manifestation of the second law of thermodynamics.  This
> sounds like a similar concept.

Orthogenetic development, or orthogenesis, is basically a concept of
evolution taking place in a concerted manner without requiring natural
selection to drive it along. The concept encompasses the idea that there
is a biological bias in mutation so that there may be a sequence of
changes that result in what can retrospectively be described as a
'trend'. Thus, the development of the mammalian ear, or the transition
from five toes to one in the horse for example, is seen as a series of
sequential mutations rather that a series of fortuitously sequential
'random' mutations that happened to appear at the right time to be
selected for through differential reproduction.

Orthogenesis was decried by Darwinians because it did not have a
'mechanism' (a bit like saying the bumble bee could not fly because
physicists could not provide the mathematical proof). A minority of
biologists saw life being structured in such a way that invoking natural
selection or drift seemed inadequate, especially when considering
speciation over broad geographic areas (Croizat). Historically, the term
orthogenesis does have some baggage because a variety of biologists
mixed the term up with teleological ideas (as Zander correctly noted),
but this was not the original intention of the term or represents its
use by other biologists.

Croizat probably developed the concept more than any other biologist by
integrating it into an overall evolutionary synthesis of space, time,
and form and the concept of vicariant recombination of characters which
may affect new or different trends. In recent times molecular genetics
has introduced concepts of molecular drive which may be concordant with
orthogenesis in some respects.

For some further reading take a look at Craw et al (1999) on concerted
evolution, and for a historical overview (which I think may be still one
of the broader comparisons) take a look at Grehan and Ainsworth (1985).
A pdf copy is available at
http://www.sciencebuff.org/grehan_publications.php

John Grehan
>
>
> >8. Natural selection is of secondary importance, pruning but not
creating
> >evolutionary trends.