> I obtained the information for my previous post from the
> writings of Brian Goodwin (primarily <How the Leopard
> Changed its Spots>), a structural biologist. Interestingly,
> Goodwin frequently uses the term "natural kind" which
> tends to make some peoples knees jerk and their eyes
> twitch :). Goodwin is sometimes accused by his critics of
> being a Platonist, which is very unfair. For Goodwin,
> evolution is first and foremost a nonlinear dynamical
> process
Yes.
> with "natural kinds" being the stable or near
> stable attractors of the process.
Well, I'd disagree ... I don't beleive that the notion
of "attractor" is well understood for complex systems,
to the point that merely using the word is arguably
incorrect.
e.g. its not obvious to me that having a large population
doesn't distort or "bend" or change the naive dynamical
equations themselves, so they are no longer valid when a
large population is in existance. Kind of like matter
bendsing space-time. Not saying that an equation cant be
found, but they are not currently understood, and thier
solutions less so. Of course, these comments are so far out
there, and I am so out of touch with current research, that
this could all be easily challenged.
> ====begin quote================================
> THE EVOLUTION OF GASTRULATION
>
> [...]
>
> NATURAL SELECTION AND THE GASTRULA
>
> A simple prediction is that the forms that failed to
> find the solution should have been eliminated. Sponges
> failed: they form an unciliated ball which then gastrulates,
> but they seem to be surviving well. Colonial organisms
> failed: they form hollow ciliated balls that do not
> gastrulate or develop further, but they, too, continue
> to survive.
I think he's getting close to the crux of the matter:
the use of the term "natural selection" colors how people
think. Perhaps a better term, that would have changed
the history of biology, would have been "selective extinction".
I.E. anything that cannot survive will die. Everything else
will live, no matter how bizzare, rational, irrational, unexplainable
it is, and form a rich variety of species, behaviours, etc.
Thus, the mistake is to talk about features that allow
organizisms to "compete better", or "metabolize more efficiently"
or whatever. While its true, its hogwash. Attention
should really be focused on the fact that in crisis situations,
it is the *lack* of an ability that determines the *lack of
survival*, rather than the inverse ("it survived better because
it was better adapted").
Its kind of like the sun orbiting the earth arguments:
hundreds of years ago, you could argue that the sun orbited
the earth: 99% of the math worked just fine, planetary motions
cnd eclipses ould be predicted just fine, etc., and the
differences between earth-around-sun vs. sun-around-earth
were philosophical. Eventually, it was realized that
earth-around-sun explained an additional 1% of bizarro planetary
motions, and overall, was a simpler mathematical theory.
But even today, you could take a terra-centric view of the universe,
and as long as you don't mind dealing with horribly convoluted math,
you can make the same predictions with the same accuracy as the
helio-centric theories.
Likewise, I beleive that saying "natural selection" is like saying
the sun orbits the earth. Instead, we should be taking about
"disaterous extinction", and how that is the true engine of evolution.
Much simpler and needs less "magic", no?
(Disclaimer: these opinions derived after watching nature
specials on TV. I am not a biologist.)
> Natural selection itself explains nothing about generative
> dynamics. Differential survival is a consequence of this
> dynamics, not a cause. Furthermore, the 'units of selection'
> are also consequences of the dynamics, the (relatively)
> stable attractors in the evolutionary process (stable life
> histories). They cannot be defined initially.
Ding! Pecisely! That's exactly the point!
(except for the remarks about attractors).
> THE DYNAMIC BASIS OF GASTRULATION
> In the course of his cytological studies, Willmer observed
> that a number of species of protists have the interesting
> property that the undergo dramatic, reversible changes of
> state, from flagellate to amoeboid, depending on whether
> they are in a low or high ionic strength medium, respectively.
> Suppose that protists with these properties aggregated to
> form a hollow ball of cells in the Precambrian oceans, as
> assumed by Buss. Such a form is a minimal energy configuration
> for such an aggregate, making reasonable assumptions about
> cell affinities, so this assumption is dynamically well-
> founded. Due to the osmoregulatory properties of cells,
> which pump ions across their boundaries to maintain
> physiological ratios of ions, the confined internal space
> of the hollow ball will have a higher ionic strength than
> the external medium. These observations therefore suggest
> that cells on the outside of the ball would tend to be
> flagellated or ciliated, while any cells that moved into the
> interior as a result of the balance of forces between cell-
> cell adhesion, compression of the ball, and spontaneous
> movement, would tend to become amoeboid, in which state they
> can divide. This is the essence of Willmer's proposals, which
> he developed in relation to the different patterns of
> gastrulation that occur in different species.
>
> Hence we have a perfectly acceptable hypothesis about the
> origins of the gastrula in terms of known properties of
> protists and the balance of forces acting within and on
> a spherical cell aggregate. Furthermore, a whole series
> of experiments are possible to explore this hypothesis
> further. One process that is not understood is the
> flagellate-amoeboid transition under a change of ionic
> strength. Some might suggest that this property is a
> consequence of natural selection. But this amounts to
> the suggestion that there must be some natural causal
> explanation of the phenomenom, and that it must be
> consistent with the dynamic stability of certain protist
> life-cycles in the context of particular environments.
> This adds nothing to a research programme attempting to
> understand generative causes. [...]
Yep. The ability to deliver this kind of support for
"my theory" is exactly why goodwin is an award-winning
biologist & I'm not ...
--linas