Did Feathers Evolve for Dispaly? We Still Don't Know!

[Michael Erickson <tehdinomahn@live.com>]

First of all, I will say that Benton et al.'s new work on the probable life 
coloration of _Sinosauropteryx_'s plumage is fabulous, and makes history as the 
first time the life coloration of a dinosaur (not just patterning, but 
coloration) has been worked out. Magnificent. So big congrats to Benton and his 
team.

But the point of this post is really something else - I am addressing the claim 
that this discovery provides convincing evidence that feathers (in this post I 
will be including protofeathers under the blanket term "feathers") initially 
evolved for display. Here are the relevant quotes from the news story Tom 
linked to:

“Our research provides extraordinary insights into the origin of feathers. In 
particular, it helps to resolve a long-standing debate about the original 
function of feathers – whether they were used for flight, insulation, or 
display. We now know that feathers came before wings, so feathers did not 
originate as flight structures.
“We therefore suggest that feathers first arose as agents for colour display 
and only later in their evolutionary history did they become useful for flight 
and insulation.”

As the paper does not seem to be out yet, these quotes are all I have to go on, 
but from them, Benton seems to be saying that the fact that _Sinosauropteryx_ 
appears to have been vividly colored in orange and white in life, this supports 
the hypothesis that feathers arose as display devices. This is what I take with 
issue with. For one thing, we don't actually know that _Sinosauropteryx_ itself 
used its feathers in display, we have no evidence for this, as orange and white 
banded coloration would serve purposes of camouflage just as well. Second, even 
if _Sinosauropteryx_ itself *did* use its vivid color patterns in display, that 
the animal had striking plumage in no way even begins to support the hypothesis 
that feathers themselves evolved for display, or at least not any more than 
that the bright and vivid plumage of many modern birds provides evidence for 
such. And the fact that many modern birds possess bright and vivid plumage has 
been known since, well, ever since bipedal Holocene apes first looked at birds, 
and long before evolution in the first place was recognized, let alone when the 
question of what bird feathers originally evolved for began to be pondered at. 
So the point is that a vividly colored_Sinosauropteryx_ does not add any *new* 
evidence to support the display hypothesis that we didn't have before.

Take this other example, if you will - Zebras possess extremely bold 
black-and-white striped fur coloration, so that predators examining the herd 
have a difficult time differentiating one potential target from another; in the 
eyes of the color-blind mammalian predator, individuals and their outlines 
disappear in a sea of stripes. Does this provide evidence that mammal fur 
initially evolved to confuse predators? No, of course it doesn't. The situation 
with _Sinosauropteryx_ and the initial evolution of feathers is pretty much the 
same.

Hence the title of my post - did feathers evolve for display? Maybe. Maybe not. 
(My own personal opinion is 'not', but that digresses, and matters little 
anyway.) The point is that the hypothesis that feathers initially evolved as 
display devices is really no more robust today than it was yesterday, or the 
day before that, or the day before that.

So there it is. We still don't know.


~ Michael                                         
_________________________________________________________________
Your E-mail and More On-the-Go. Get Windows Live Hotmail Free.
http://clk.atdmt.com/GBL/go/196390709/direct/01/