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Bristles before down: A new perspective on the functional origin of feathers

Ben Creisler

A new online paper:

W. Scott Persons IV and Philip J. Currie (2015)
Bristles before down: A new perspective on the functional origin of feathers.
Evolution (advance online publication)
DOI: 10.1111/evo.12634

Over the course of the last two decades, the understanding of the
early evolution of feathers in non-avian dinosaurs has been
revolutionized. It is now recognized that early feathers had a simple
form comparable in general structure to the hairs of mammals. Insight
into the prevalence of simple feathers throughout the dinosaur family
tree has gradually arisen in tandem with the growing evidence for
endothermic dinosaur metabolisms. This has led to the generally
accepted opinion that the early feather coats of dinosaurs functioned
as thermo insulation. However, thermo insulation is often erroneously
stated to be a likely functional explanation for the origin of
feathers. The problem with this explanation is that, like mammalian
hair, simple feathers could serve as insulation only when present in
sufficiently high concentrations. The theory therefore necessitates
the origination of feathers en masse. We advocate for a novel origin
theory of feathers as bristles. Bristles are facial feathers common
among modern birds that function like mammalian tactile whiskers, and
are frequently simple and hair-like in form. Bristles serve their role
in low concentrations, and therefore offer a feasible first stage in
feather evolution.