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Re: Size and Extinction (fwd)



Larry wrote:
> 
> That means that 99.9% of all life forms were "failures."  

        You make it sound so judgmental.  Yes, all species evolve to a 
point--at some point in space (geographic or morphologic or both) and 
time they are going to run up against some sort of environmental stress 
that they cannot cope with ( Elephant dentition enamel is a perfect 
example).  At that point they begin to fail, that is they become rare.  
An organism going extinct is random.  When the Calf. Condor goes out it 
is going to be because some tech drops the last egg--it is random.  The 
issue is when did the condor become rare in the first place.  Species 
become rare because they do not experience the correct chance mutation in 
the genotype to cause the correct phenotypic expression to enable them to 
handle what the environment is dishing out.  They fail.

> 
> Dinosaurs disappeared BECAUSE they were adaptable.  They radiated out 
> gloriously becoming extreme specialists just as you advocate, but weren't 
> generic enough to make it when the ol' exploding bolide from outer space 
> paid them a call.  

        Let us have this conversation in ten years when there is some 
sort of conclusive evidence that the boilide caused the extinction.  
There simply hasn't been enough good work done on this issue to be able 
to make these gross generalizations.  It is speculative.

> 
> Including such bolides from outer space in the category of "normal 
> stresses of evolution" is analogous to saying that you won't buy a car 
> because it's not structurally strong enough to withstand meteor impact.  
> I think your day-to-day priorities, like the dinosaurs, are a bit 
> different.  I personally would not blame you if you opted for, say, fuel 
> efficiency or boss woofers or great 0 to 60, and would think asteroid-car 
> man was a bit odd.  Wouldn't you?
> 
        Listen, nothing makes any sense if taken out of context.  
Analogies and explanations only work if they are qualified by 
establishing parameters beyond which they are not valid.  If one of my 
students leaves the university and fails to graduate, whether or not he/she 
"went extinct" depends on why he/she left.  If he/she left Penn because 
he/she was hit by a car or got cancer, that is not extinction (but it is 
analogous to the sun becomming a red giant) A student only "goes extinct" 
if he/she "fails out" because of an academic reason.  The Ivy League is a 
tough place, there are high attrition rates-academic attrition rates.  Of 
course if an asteroid blew the planet into bits the species didn't fail.  
We are talking about extinction here, not extraterrestrial genocide.

        However, if a student doesn't survive calculus or physics they 
either didn't work hard enough, they don't think the same way the system 
forces them to, or they are not bright enough (ASSUMING NO EXTERNAL 
INFLUENCES LIKE CANCER).  Any of these three reasons is a lack of fitness 
for the student to pass the course.

        Taken even further (assuming this analogy can go this far), I 
know friends from college who had 4.0 GPAs, walked into the best graduate 
programs in the country and fell flat on their faces because they 
couldn't synthesize--they were rote machines.  They became extinct in the 
academic game because the environment changed to a degree that they could 
not adapt to.  They "failed" to adapt and they went extinct.

        And, extreme adaptation into tight, little boxes of the 
ecological regime means that the organism is really good at what it 
does.  If, however, the thing cannot adapt to the changes that go on 
around it, it is still a failure in the evolution game.  Just because an 
organism is really good at something (AT A GIVEN POINT IN SPACE/TIME) 
does NOT mean that it is going to make it as long as the cockroach has. 
Only the strong surviving is probably over simplifying things.  Only the 
strong and adaptable survive.  In some cases only the strong and quickly 
adaptable survive.  

        Yes, 99.9% of everything that has ever existed on this planet is 
dead in a phylogenetic sense.  Yes, that does mean that they failed to 
adapt at some point.  That allopatric speciation might have allowed the 
phylogenetic lineage to occur is not the issue.  The fact that birds are 
still around and theropods are not is fine.  But the simple fact that 
birds are extant doesn't change the issue that the Theropoda sensu 
stricto is not.  The theropods failed.  It doesn't mean that they were 
failures in what they did--they weren't.  It does mean that they failed 
to adapt at a point and got selected out of the game.  Nature doesn't 
care how good you were in your past.  If you are not cutting the mustard 
now, you get fired without a pension.  There is no tenure.

  


-- 
__________________________
Josh Smith
Department of Geology
University of Pennsylvania
356 Hayden Hall
240 South 33rd Street
Philadelphia, PA  19104-6316
(215) 898-5630
smithjb@sas.upenn.edu