Feather Evolution

[Thom Quinn <swo@execpc.com>]

Would love feedback on this.

TQ
---------------------------------------------

 
An alternative hypothesis on the informational origin of feathers and
their original function 

Thomas Quinn
University of Wisconsin-Madison
P.O. Box 510373 
New Berlin, WI 53151

thomquinn@esosoft.com

Abstract

Understanding the origin of the feather is perhaps one of the most
important aspects in the evolution of the class Aves; it is also the
most problematic. Although good fossils of very early birds have been
recovered, clear proto-avian fossils are almost non-existent. The
feather is a structurally complex biological phenomenon that could have
only evolved once; therefore, unless taphonomic events happened at
exactly the right times, the undiscovered fossil record of ancient
feathers is very limited. Without the feather impressions associated
with Archaeopteryx, it would have been classified as a late Jurassic
reptile instead of the earliest known bird. As a result, researchers
must rely on theoretical biology to analyze the origin of feathers for
the moment. While most biologists agree that the feather evolved from
the reptilian scale, there is debate on how this occurred. Both
locomotion and thermoregulation have been suggested as the most probable
selection forces behind feather evolution. Unsurprisingly, the feathers
of extant birds have three main functions: locomotion, thermoregulation,
and communication. Communication is often considered only a secondary
function of specialized feathers, an idea that should be re-examined. It
is very possible that the earliest proto-feathers were primarily used
for various information-based behaviors such as sexual signals, warning
signs, territorial cues, or threatening stances. Proto-feathers could
have evolved quite rapidly because simple morphological alterations
could have augmented the size or shape of the pre-avian scales; the very
first feathers were nothing more than modified, elongated scales. I
propose that communication factors were responsible for the initial
shift from scales to feathers. Those animals that had longer, wider, or
novel scales could have conveyed specific messages more effectively,
thereby increasing their overall fitness. Creationists are quick to
point out that "half a feather" would not be useful for true powered
flight or insulating obligatory endothermic animals, but even small,
differentiated scales (i.e. size, shape, shading) would have allowed
these pre-avians to communicate visually with one another. This
alternative hypothesis would mean that the primary features of modern
feathers, locomotion and thermoregulation, are historically secondary
functions. It should be noted that the long feather-like structures
found on Longisquama, a middle Triassic thecodont and the contemporary
of the elusive proto-bird, were likely used for informational displays.
The various markings, color patterns, secondary structures, and
communication behaviors of modern reptiles strengthens the validity of
this hypothesis.