Re: scales to feathers (was Dinogeorge Digest #7)

[Betty Cunningham <bettyc@flyinggoat.com>]

I was assuming the left side of a scale was a mirror of the right side
of the scale. And then I assumed it would continue to be symmetrical
when mutating into a feather. 
 Is it NOT the case that scales are symmetrical?  
I also assumed there would be one form of protofeather before it veered
off into specialisations, rather than having it redevelop anew several
times.

-Betty Cunningham

Dinogeorge@aol.com wrote:

> Actually, nature >hates< symmetry: >perfect< symmetry, that is. Every
> bilaterally symmetric organism has asymmetrically arranged internal organs or
> organelles, and every bilaterally symmetric organism is externally at least
> slightly different from left to right.  And this is not to mention the
> molecular asymmetry of life's building blocks, such as amino acids, DNA,
> proteins, sugars, and so forth. Undoubtedly, this stems from the simple fact
> that there are many, many more ways to be asymmetric than to be >perfectly<
> symmetric, so even when the environment works to constrain the evolution of
> asymmetry, it doesn't go away completely.