progressive evolution

Richard Gordon gordonr at cc.UManitoba.CA
Sun Jun 25 18:11:01 EST 1995


In response to the comments below, I'd like to note that here are two
different objections to the term "progressive evolution" that have to be
distinguished: 

1) evolution is going nowhere, and so can't be labelled progressive;
2) evolution is stochastic, so while complexity may, on average, increase 
over time for some lineages, which ones progress and in what ways cannot 
be predicted with precision.

The first notion stems from the New Synthesis idea of evolution as shifts
in frequencies of alleles, a process that is generally regarded as
reversible. The second notion stems from the idea that ratcheting or
irreversible processes occur in evolution, sometimes labelled
non-Darwinian evolution. Can we identify irreversible mechanisms in
evolution that can be shown to be important? 

If the answer to my last question is yes, then evolution is indeed, on
average, going "somewhere", with the same inevitability with which frost
grows on a window pane under the right (irreversible) conditions. True, we
can't predict the exact frost pattern in advance, but we can predict that
frost will cover the window, and a covered window is indeed a sight to
behold. Whether one beholds it in curiosity or religious awe I suspect is
a bit beyond the theory of evolution itself. Science, if it is ultimately
reducible to anything like math, will have its undefined terms and basic
axioms, and one's attitude towards these can range from further analysis
to religious. At any rate, we are far from having reached this level of
explanation in biology, so a little humility is warranted. If a
creationist wants to believe that God put irreversible processes in place
so as to produce complex organisms after a while, which turned out to be
(not inevitably) us, what is wrong with that? That's a far cry from
claiming scientific support for a universe only 5755 years old. If we give
up our humility under pressure from creationists to appear certain of
ourselves, we end up producing dogma, not science. 
-Dick Gordon, U. Manitobs[Jun25,95]

On Tue, 20 Jun 1995, Phillip Bigelow wrote:
...
> I don't like the subliminal ramifications of calling the
> effect "progressive", because it imparts some divine pre-destination, or
> some type of religious meaning to evolution.  At best, the term "progressive
> evolution" is anthrocentrically-perjurative.  It also implies that life
> is progressing toward "something".  Of course, none of these inferrences are
> scientifically-supported in any way.  Yet, the term is still used in 
> scientific journals, and appears to be accepted. 
>   It seems preferable to re-name the phenomenon.  We are dealing with a
> semantic issue here, not a scientific one.  As a replacement term for
> "progressive evolution", why not use the term "temporal-complexity
> evolution", since the observed complexity of the phylogeny of any
> one tree theoretically increases with time. 
>   Evolution theory already has a bad rap in the eyes of the public.  Let's not
> give creationists any more ammo by using anthrocentrically-bias terms.
>  
On Tue, 20 Jun 1995, Richard M Kliman wrote:

> I take it you use "progressive" to refer to an irreversible increase in
> complexity of the body plan, attributable to an increase in the number
> and combinations of transcription regulators.  This is fine (though I
> wonder where paedomorphosis fits into the picture - would this be
> temporarilty digressive evolution?).  It's still fair to say that some
> relatively simple organisms are apparently quite successful, though many
> of them have apparently evolved in a progressive manner (using what I
> infer to be your definition).
>
> The use of the word "progressive" that I have trouble with is that which
> implies a starting point and a goal....




More information about the Mol-evol mailing list