[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Extinction of Dinosaurs



LN Jeff writes:

>     Hence the further improvements to the design.  No, a species does 
>not "think ahead" when it is evolving, but if the system it has could be 
>better, it will make modifications that are IMMEDIATE improvements to the 
>design.  

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.

>     Its important to keep in mind that the features of Archaeopteryx that 
>made it a relatively poor flier compared to modern birds were ALL PRIMITIVE.  
>The lack of a big breastbone, pygostyle, triosseal [sic?] were ancestral 
>theropod features, not features that might have been DERIVED to keep 
>Archaeopteryx a relatively crappy flier because this was somehow more
>advantageous to the lifestyle its ancestors began to adopt than being a 
>better flier. 

What is more important (given that many later birds became far 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.
--
Ronald I. Orenstein                           Phone: (905) 820-7886 (home)
International Wildlife Coalition              Fax/Modem: (905) 569-0116 (home)
Home: 1825 Shady Creek Court                  Messages: (416) 368-4661
Mississauga, Ontario, Canada L5L 3W2          Internet: ornstn@inforamp.net
Office: 130 Adelaide Street W., Suite 1940    
Toronto, Ontario Canada M5H 3P5