From: julian@fraser.sfu.ca (Julian Shillcock)
Subject: Re: behavior and evolution
Organization: Simon Fraser University, Burnaby, B.C., Canada
Date: Sun, 16 Aug 1992 22:46:14 GMT

colby@bu-bio.bu.edu (Chris Colby) writes:

>In article <julian.713910132@sfu.ca> julian@fraser.sfu.ca (Julian Shillcock) writes:
>>Thanks for the references, I'll see if the university library has them,
>>and whether I can understand them( not a given!). I am reading a book
>>on the brain called "Corticonics:Neural circuits of the cerebral cortex" 

>[much about lack of knowledge of brain workings deleted]

>Yes, I'm fairly sure nobody has a good working model/theory of
>how the brain works. But, that doesn't mean that evolutionary
>biology cannot make any predictions about behavior -- because
>explanations of behavior can fall into two catagories: proximate
>and ultimate. The first would try to explain the behavior in terms
>of neurotransmitters and neural architecture; the second would try
>to explain a behavior in terms of it's adaptive value.

>Let me give a quick example: Male bluegills (a fish) have two
>reproductive strategies. These are genetically based(*). One type
>of male matures slowly(**), but eventually reaches a large size and
>attempts to guard a harem of females. The other type matures
>quickly(***), but is much smaller and "sneaks" matings. They wait until
>the females drop the eggs and swim by before the territorial male
>can fertilze them.

>(*) ~30 percent of the male offspring from territorial males are
>"sneakers", ~50 percent of the male offspring from "sneakers" are
>"sneakers". Obviously more that one locus controls which phenotype
>is produced -- the behavior type appears to be fixed rather than
>conditional (i.e. the fish can't switch behaviors).
>(**) six years until reproductive
>(***) two years until reproductive

>Now, somebody might be working on the proximate mechanisms of this
>behavior (although I doubt it) -- but evolutionary biologists find
>it much more interesting to examine the ultimate causes of this
>behavior. In other words, how do these two behaviors coexist in
>the same species? Why doesn't one reproductive behavior type
>outcompete the other? And yes, biologists use mathematical
>models to figure these sorts of things out. The answer is, at a
>certain frequency of territorial males to sneakers, both
>reproductive strategies have the same average fitness. Alcock
>gives the basics of this in his book, check the references for
>the gory details.

That is a fascinating example. It recalls a type of equation I came
across called the predator-prey model (or Rabbit-fox). It deals
with how two species compete for available resources. I can
quite understand why biologists would concentrate on these mechanisms
because one can actually predict things now, and make models.
Also, the predicitve power of a neuronal model is  (I think) going
to be severly limited at a macroscopic level. Rather like the
quark model of nuclei being useles for predicting chemical properies
of crystals.

>My point is that we don't need to know how something works to
>produce theories as to why it works.

Agreed.

But do evolutionists believe that everything will ne day be
explicable by the current (or slightly modified) theory of evolution?
Is it no more likely that there will occur some paradigm shift
(like physics went from Newtonian absolute space to Einstienian
relativity) in which our current understanding will be seen to be
an approximation? I say this because I wonder whether some
arguments against a divine intervention in nature spring more from
scientist's world-views than a sound deduction from science.
I do not reall yunderstand how seriously to take evolutionism's 
claim to explain "everything" we observe ( I should say
some evolutionists' claim). It sounds more like an unjustified,
but simplifying extrapolation.

julian
 
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