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Re: birds scales




On Fri, 8 Dec 1995, Rob Meyerson wrote:

> Then again, it may mean exactly that.  To go out on a limb (and I think
> I hear it snapping:-), since down is found mostly on chicks, this may 
> show that it is a primitive feature (based rather loosely on the 
> principle of neoteny). > 
> Rob
> 
> 
 "Principle of Neoteny"?, Neoteny is not a principle of evolution, it is 
a process that sometimes occurs in evolution. It results in the 
retention of juvenile structures of an 
ancestor in the adult of a descendant, more specifically acheiving this 
affect by retarding the rate of ontogeny. Therefore the appearance of 
down in the juveniles of modern birds is not an example of neoteny. I 
think you may have been confusing neoteny with "recapitulation" where the 
ontogeny of an organism (or a structure of an organism) mirrors the 
evolution of that organism (or structure). Ernst Haekel thought that 
recapitulation was universal to all organisms and labelled it the 
"biogenetic law", this was popular last century but was well out of 
favour by the begining of this century.  

Adam Yates