Re: protofeathers

[TomHopp@aol.com]

In a message dated 6/3/99 3:41:50 AM, brush@uconnvm.uconn.edu writes:

<< In theory, whatever the first structure, and I argue that it may have been 
simply a structure similar to a barb that grew continually (which BTW could 
describe the situation in Sinosauropteryx). Subsequent changes that produces 
pennaceous or plumulose feather parts which were organized into the existing 
morphologies, are simply the breaking of symmetry in the follicle and 
differential growth rates. These 2 factors alone gave rise to all the 
modification of the basic morphology. Further, and this is more speculative, 
I posit that the most direct way to increase design complexity is to simply 
fuse these structures (barb homology (?) at their bases. That coincidentally 
produces the morphology of natal down. >>

Yes, but . . . .

Couldn't a single barb growing continuously just as easily be termed a hair, 
not a feather? Isn't there a major distinction between these two structures 
based on the branching nature of a feather? What drives the branching? A 
"branching" gene(s), of course, but when did it (they) arise? Before or after 
feathers got long?
    Imagine a very short scale that, for some reason, frays at its tip, to 
yield an animal covered with a scaly-but-fuzzy coating (for whatever purpose 
I can't imagine). This frayed-scale creature might require all of the 
branching that goes into a much more elaborate feather, at a time BEFORE the 
lengthening process had begun. If it had different amounts of branching on 
different parts of its body, voila -- different feather types before you 
would even want to call the things feathers. That was my point, not 
necesarily in opposition to other points, just focused on the order in which 
the genes for feather branching versus length appeared.
--Tom Hopp