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Re: Extinction of Dinosaurs



> No, that isn't the way it works.  First of all, animals don't "make
> improvements"; mutations arise which persist if they are advantageous, no
> matter which direction they lead including full reversals of prior
> advantageous mutations.  A mutated wing will persist in its mutated state if
> it is advantageous, regardless of whether it is a "better" wing or not.
> There is no such thing as the inheritance of acquired characteristics; an
> animal cannot come up with an improvement that it, as an individual, was not
> genetically programmed to possess and pass it on genetically to its offspring.

     I'm not talking about Lamarkism.  Yes, there are lots of different 
mutations, but they don't all stand the test of time in the gene pool.  Only 
the advantageous ones (or at least the ones that aren't hurting anything) 
persist in the population.  The others are weeded out.  This is what I 
mean by improvement. Not of the individual, but of the population.

> What is more important (given that many later birds became worse fliers 
> than Archaeopteryx) is that when Archaeopteryx evolved the niche for flying
> crow-sized vertebrates was a comparatively unexploited one, with few
> competitors around, so that a non-flyer could develop into a poor flier.
> Today that is highly unlikely to happen because, despite the loss of the
> pterosaurs, the niches for flying vertebrates are heavily occupied by
> excellent flyers and that avenue for evolutionary expansion is probably
> largely closed.

     Case in point.  Those EXCELLENT fliers didn't start out that way.  
Early birds continued the trends seen in an earlier stage in 
Archaeopteryx.  
         
LN Jeff
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"Fetch Dogbert!"
KABLAM!!
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