Origin of feathers

[Jonathon Woolf <jwoolf@erinet.com>]

Random musings . . .

With all this stuff about dinobirds in the news, I was thinking about
the origin of feathers, and how they might have developed from the fuzz
that _Sinosauropteryx_ seems to have had.  Looking over all the
explanations that have been suggested, it occurred to me that all of
them have been mundane explanations focusing on feathers as an organ
that _did something_: insulation, gliding, etc.  IOW, an organ that had
some practical use. But I don't find any of these suggestions really
convincing, mainly because they don't answer the 'what use is half a
wing" question.  Granted that a wing is useful for flying _after_ it's
developed to a certain point, and a feather can be shaped into an
airfoil _after_ it's reached a certain size.  But what got the wing and
feather to that point?.

Hence, a different thought: maybe feathers developed not as an organ
that _did_ something so much as an organ that _showed_ something --
i.e., a courtship or territorial display of some sort.  Something
similar may account for ceratopsid head shields and sauropod tails, so
why not protobird feathers?  Bigger, brighter feathers = more chances to
mate, thus you get long feathers through sexual selection.  Long
feathers catch air, producing a useful gliding surface for small,
tree-dwelling theropods. After that, natural selection shapes the
feathers and wing into airfoils.

Sounds plausible to me.  What do y'all think?

-- JSW