Me again on Evolution

Brad Swanson bswanson at bilbo.bio.purdue.edu
Wed Jan 18 14:51:59 EST 1995


In article <D2K57F.88K at ssbunews.ih.att.com>, ian at happy.milkyway wrote:

> I'm a little taken back at the slant on Darwinism. "Fit" is a very
relative thing
> most easily viewed in retrospect.
>"Fit" is not necessarily (or even likely) related
> to "Fight" -- "Fit" applies to reproduction -- carrying the genes on
through the
> time in the genome -- nothing else. We have also come to understand that
"over-
> specialization" can be the downfall of a species -- since the
environment (physical,
> boilogical, social) changes over time and sometimes in dramatic and
unexpected ways,
> what appeared to be a useful adaptation may prove to be a species downfall.

You have a rather major flaw in your evolutionary thinking here.  No
organism is going not "produce" an adaptation because it might be
deleterious in the future.  No organisms cna see in to the future to
determine what will be good or bad.  They will however "produce" an
adaptation that will allow them to increase their survival/reproductive
success in the present.  It doesn't matter if the trait will be bad 200
years from now or even 20 years from now.  If it helps that organims to
increase its reproductive success in the present the trait will arrive and
thirve until the environment does change.  a trait can even arise if it
has a deleterious affect during the life time of the organism, as long the
deleterious effect occurs after the organism has passed reproductive age. 


You also seem to be supporting a group selectionist argument by talking
about "a species downfall".  The individual doesn't "care" if a trait it
brings about leads to the species down fall, natural selection will still
favor the trait if it increases that individuals reproductive success
relative to its conspecifics.  Remember that selection works at the level
of the individual (I'm not trying to stir up a level of selection debate
here), not the group or species (although others will say selection works
at the level of the gene).


 We
> are also becoming aware that evolution is not simply a genetic dance,
there are
> other mechanisms acting on the reproductive viability of species which
ultimately
> are reflected in the gene pool.

For selection to work though, the trait has to have three components,
variation, heritability, and an influence on reproductive success.  If a
trait lacks any of these three components it can't be influenced by
natural selection.  Evolution can still occur if there is at least
variation, but it will be altered either by genetic drift, gene flow or
mutation, so I don't understand what you mean by evolution not being
simply a genetic dance.  True most traits will have an environmental
component to them though.

 Patterns of behavior may not be genetically related, 
> but would seem to undergo similar selection.

Actually, you might be surprised how much of behavior has a genetic component.

> 
> Bottom line -- survival of the fittest is easily misinterpreted -- you
and I will
> not be the judge of "fitness" -- time will be. Diversity is the only
hedge against
> extinction and it is not an individual thing its a population
phenomenon. I would
> suggest that trying to beat the odds is the surest path to extinction!
> Ian

Again, though, if decreasing diversity increases your reproductive
success, natural selection will favor that trait, regardless of what it
may cause in the future


cheers,
Brad

-- 
Brad Swanson                  ***The ratio of my incompetence ************ 
Dept. of Biology               ****to the task at hand isinfinite!*******
Purdue Univ.                    *** Graduate school, the last legal*****
bswanson at bilbo.bio.purdue.edu    ****form of indentured servitude******



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