Re: Joel and Bryant /talk/
Bryant (mycol1@unm.edu)
25 Aug 1996 11:38:39 -0600
In article <321F53EA.1CDC@best.com>,
Joel and Lynn Gazis-Sax <gazissax@best.com> wrote:
>Bryant wrote:
>
>> No, I didn't mean that. Evolutionary biology has progressed without
>> paying much attention to Gould. But what he has done is present the
>> public with an inaccurate view of the field of evolutionary biology.
>
>I think that it did pay attention to Gould! Why then all the articles
>which have been published in various magazines criticizing him. Gould
>does not sound like someone whose word has not been taken into account
>at all by his peers.
Well, he has openly criticized most evolutionary biologists
("adaptationists") in the popular media. That got their attention. And
the vision of evolution Gould pushes--one in which natural selection and
the generation of adaptations is not king--is far from the general
evolutionary paradigm. So he has critics, yes. But that doesn't mean
that the points he makes such a big deal of in his public press essays
have fundamentally changed how darwinists look at their field.
>* The notion that natural selection is responsible for new species.
Do you mean to say that Gould came up with the notion that speciation is
due to natural selection? Or that he criticized it?
>What it /did not/ create, however, were the genes that made the chihuahuas
>small and the Great Danes big. How did these come about? Through mutation
>and similar DNA level processes.
Which were then *selected* (artifically, by human breeders) to favor the
passing on of certain traits in a given lineage.
*All* evolutionary change begins with mutation. The question is whether
that variability is subsequently acted upon by selection or not.
> The only way that natural selection could
>come up with changes that turned one offspring somewhere back in the time of
>the first mammals into a herbivore and another into a carnivore would have
>necessitated some kind of Lamarckian instrument. And we all know that Lamarckianism
>doesn't work.
Um, yes we do. Which makes this sort of silly--no modern adaptationist,
no darwinian, claims what you propose here.
>Natural selection acts on populations, not on the genes.
That is incorrect.
Natural selection acts on individuals, and thus (indirectly) on gene
complexes. *Evolution* (changes in allele frequency) occurs at the
population level, and often reflects the collective results of selection
on a population's individuals' reproductive successes and failures.
>Gould calls natural selection a secondary process in evolution because it
>does not cause the primary changes itself. It only takes what is there and
>winnows out the bad. That's all. The real cause of change is mutation. That
>is what works at the primary level.
That's well accepted. But few complex traits (hearts, brains,l thumbs)
can be attributed to mutation alone; they're the result of selection,
favoring individuals with some traits over others, through deep
evolutionary time.
>Here's some evidence for this operation: Consider the massive species dieoffs
>which occur every few thousand years. Towards the end of one of these, we find
>that there is lots of diversity out there and extreme specialization to fit
>into niches.
There are not mass extinctions every few thousand years. There have only
been 5 mass extinctions that we know of from the geological record in the
entire history of life on Earth (~3.5 billion years or so).
>Then something happens (currently that something is called "humanity"
>:) ) and many species, except for generalists, die off. Then the process
>starts all over again. How do generalists turn into specialists? How did the
>Koala, a classic specialist which can dine on eucalyptus leaves which kill other
>animals, get that trait which allows it to store the poison out of harms way?
>How could natural selection /do this/?
Only natural selection *could* adapt Koalas to metabolize their host
plants' chemical defenses. The alternative forces of evolution do not
create "purposeful" design. Only selection does that.
Mutation allowed some lucky Koala the ability to digest this abundant
food (eucalyptis leaves), and that lucky koala's genes became, through
time, better represented than the genes of koalas who didn't have access
to this dietary resource. That's natural selection.
>What Gould simply points out is that somewhere in
>the past a Koala ancestor got lucky: it developed a gene that let it eat the eucalyptus
>leaves. And because there were lots and lots of eucalyptus around, it could
>survive.
And reproduce. Gould shouldn't be credited with a system of thought
simply because he sometimes subscribes to it. You just described natural
selection. Gould appears to believe that natural selection is not the
major player in evolution that most other evolutionists believe it is.
He prefers to point to drift and phylogenetic/developmental constraints
that all evolutionists give a nod to but don't bow before the alter of.
Bryant
|