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Re: Bird reduce their "heating bills" in cold climates
Jura <firstname.lastname@example.org> wrote:
> There are some good evo-devo reasons to assume that the
> transition scales to feathers was an all, or nothing kind of
> affair (well, scales to filamentous stuff at least).
I thought that there was good evo-devo evidence that this transition did not
take place at all. Instead, work by Prum and Brush indicates that feathers are
evolutionary novelties, and did *not* evolve from scales.
"Over the last half of the 20th century, neo-Darwinian approaches
to the origin of feathers, exemplified by Bock (1965), have
hypothesized a microevolutionary and functional continuum between
feathers and a hypothesized antecedent structure (usually an
elongate scale). Feathers, however, are hierarchically complex
assemblages of numerous evolutionary novelties - the feather
follicle, tubular feather germ, feather branched structure,
interacting differentiated barbulesâthat have no homolog in any
antecedent structures (Brush 1993, 1996, 2000; Prum 1999).
Prum, R.O. and Brush, A.H. (2002). The evolutionary origin and diversification
of feathers. Quart. Rev. Biol. 77:261-295.
Prum. R.O. (2005) The evolution of feather diversity and function: Exaptation,
functional redundancy and historical contingency. In: Briggs, D.E.G. (ed.)
Evolving Form and Function: Fossils and Development. pp 245-256.