Re: Origin of feathers

[Dinogeorge <Dinogeorge@aol.com>]

In a message dated 98-04-09 05:49:30 EDT, tonyc@foe.co.uk writes:

<< It has been tested with frogs - females (I forget which species) were
 found to respond more strongly to artificially constructed male vocal
 calls than to those of their own species - the artificial calls were
 based on natural calls with added complexity.  Although neither these
 frogs nor their ancestors had ever encountered this call, it was immediately
 more sucessful at attracting females.  This suggests that sexual selection
 may favour elaboration of display structures/behaviour,
 maybe accounting for peacock tail-type phenomena.
 
 Therefore, if therapods were already using forearm displays, any chance
 mutation which increased the visual stimulus could  be favoured
 by sexual selection, if the opposite sex were attracted to the most visually
 arresting forearms (or whatever). >>

Even if you can extrapolate from frogs to theropods, this is, as you note, the
>elaboration< of an >existing< structure or behavior. What I'm talking about
is the cause of the initial appearance of pre-feathers, where previously there
were none. The need for new display features isn't specific enough to compel
the initial appearance of feathers. "Display" is a catch-all default cause to
justify the appearance of a vast array of structures that seem to have no
other reason for their existence.

When pre-feathers first appeared, it is likely (though not certain, of course:
perhaps they popped into existence fully structured, with rachis, barbs, and
barbules!) they were small (like hairs) and thus had little impact on the
visual appearance of the animals. The visual impact would have come later, and
would have gone hand-in-hand with the enlargement and elaboration of the pre-
feathers.