On Mon, 5 Apr 2004 05:22:05 +0000 (UTC), 
Jeffrey Turner  wrote:
> Larry Moran wrote:
>> Jeffrey Turner  wrote:

[snip]

>> I suspect the real problem is yours. You are confused about the 
>> difference between "spandrels" and random genetic drift as a 
>> mechanism of evolution.
> 
> Random genetic drift doesn't occur fast enough to account for very
> much in evolution.  You have yet to seriously challenge my assertion
> on that.

Let's consider the simple case of neutral alleles becoming fixed in
a population by random genetic drift. The rate of substitution (K) of 
neutral alleles in a population is equal to the mutation rate (u).

                        K = u

Note that the rate of substitution is independent of population size.
This result has been discussed many times on sci.bio.evolution and it's
well-described in the textbooks.

Let's see what this means for mammals with a genome size of 3 billion
base pairs per haploid genome. If the mutation rate is 10^-9 per base 
pair in each generation then the overall mutation rate per diploid 
genome is about 6 mutations per generation. Thus, in a typical mammalian
species there are about 6 new alleles becoming fixed in the population
by random genetic drift every single generation. 

Is that fast enough for you? How does it compare with the overall rate
of fixation of alleles under natural selection? I assume you know that
number or you wouldn't have made your claim.

(Note, there are many simplifications in such population genetics models
but the basic point is valid. It may take a long time for any one mutation
to become fixed but there are so many alleles that the net overall effect 
of chance processes is quite remarkable. The quoted rate includes 
mutations in junk DNA - we could adjust for mutations in codong regions 
genes by dividing by 100.) 

>>>Leaving aside the issue of random drift, I'd say that a new species 
>>>just has to have an edge on the previous species - it doesn't have to 
>>>be finely wrought in every particular.  
>> 
>> Why does a new species have to have an "edge" over
previous species?
> 
> Because of competition for resources.

You are assuming the very pan-adaptionism that you deny. The fossil 
record shows that in most cases when a species splits in two, the 
two species co-exist for millions of years. That's the essence of 
the punctuated equilibria pattern described by Eldredge and Gould.

Over time, some species survive and others don't. The reasons for
this differential survival are hotly debated. It may be that one
species has an adaptive advantage over its sister species. Or,
it could be that one species just happens to survive by chance. 
Gould discussed these possibilites in "The Structure of Evolutionary
Theory." He believes that chance must play a major role ...

   "The analog of genetic drift - which I call 'species drift -
    must act both frequently and powerfully in macroevolution.
    Most clades do not contain large numbers of species.
    Therefore, trends may often originate for effectively random 
    reasons."  (p. 736)

>> This isn't the current consensus amoung those who study speciation.
> 
> Oh?  What gibberish are you paying them to teach these days?

The current models of speciation emphasize allopatric speciation as
a major player. When species arise as a result of geographical
separation they do not directly complete for resources. Thus,
there is no requirement that the new species has to have an "edge"
on the previous species. You seem to be confining your thoughts 
to a particular form of speciation where a parent species gradually
transforms into a new species over time with no splitting. At least
I think that's what you mean.
 
>> Do you know something about the subject that they don't? If so, 
>> please let us in on it.
> 
> I keep telling you and all you can produce is that your bishops are
> in disagreement.  It is as if you are trying to build an Earth-
> centered cosmos in a post-Keplerian world.  This is understandable.
> The more complicated the cosmology, the more niches there are for
> theories and papers.  Out of enlightened self-interest everyone
> nods and winks at everyone else's "theories" because fools like you
> enforce a "publish or perish" environment.

I take that as a "no." You don't know very much about the subject but
you want to use this discussion to get up on a soap box and rant
about the evils of basic research.

>>>After sufficient time the species that inhabits a given niche will 
>>>be superior in all relevant aspects to anything else that might be 
>>>possible with modest mutations - so the ear-size of elephants is 
>>>optimum for them, but there either hasn't been time or isn't a 
>>>suitable pathway to bring the egg-size of a kiwi bird down to
>>>something less than one-quarter the size of the mother kiwi.
>> 
>> I'm glad you're not a pan-adatiopnist. I'd hate to think what you
>> might write if you were!
> 
> I'm glad I'm not an administrator or heaven knows what garbage I'd
> write.

What the hell are you talking about?




Larry Moran
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