Re: Feathers for S excretion...and tennis balls

["Steve Brusatte" <dinoland@lycos.com>]

On Sat, 31 Mar 2001 16:26:57  
 T. Mike Keesey wrote:
>On Sat, 31 Mar 2001, Steve  Brusatte wrote:
>
>> Erm...this may be pressing it.  As far as I understand, hair evolved
>> from sensory bristles in early mammals.
>
>As I understand it, the earliest evidence for hair in _Synapsida_ is
>supposed whisker pits in basal _Cynodontia_. This doesn't mean that hair
>evolved from sensory bristles -- it could easily be the other way around,
>since senory bristles are one of the few types of hair that leave skeletal
>indicators. Someone correct me if I'm wrong here.

Oh, sure it could be the other way around.  I was just saying "as far as I 
understand," which means "based on the papers I've read."  Sensory bristles 
could have easily evolved from hair...perhaps bristles are specially modified 
hairs.  I doubt there will ever be good enough fossil evidence to base any 
concrete theory on, though.  I was just basically expressing my cynicism, my 
doubts about the sulfur hypothesis.  

In response to David, who asked me which "physiological factors" I mentioned in 
my first post: by this I don't mean sulfate production (HP Tom Hopp has summed 
this up nicely, and a Cornell Medical School graduate is much more of an 
authority on the subject than I am :-)  I was simply talking about the kidneys. 
 Kidneys seem to suffice in modern mammals, even insectivorous ones. Do 
insectivorous mammals have more hair than carnivorous or herbivorous ones?  Is 
the hair of insectivorous, and therefore sulfur-ingesting, mammals more laden 
with sulfur than the hair of carnivorous or herbivorous mammals?  I don't know 
if this is of any value...and I doubt if there are any publications based on 
these questions.  Feathers, especially elaborate ones, seem to be too expensive 
in a biological sense to be a dump for sulfur, an element that seems to be 
handled well by the kidneys.  I really DON'T KNOW, though, as I'm no authority 
on this.  

Okay, now onto the tennis balls and bird feathers.  Although I am probably 
nowhere near as good as HP Jim Cunningham (I did win my conference title last 
year, though) , I am also a tennis player.  The "fuzz" on tennis balls is 
specifically designed to promote spinning and trick shots and such.  That's 
why, as Jim said, you can't keep using the same tennis ball forever.  Feathers 
are probably much of the same.  Feathers don't make birds fly extremely fast.  
Airplanes and missles fly at amazing speeds, but neither has any structures 
analogous to feathers.  If the purpose of feathers was to provide incredible 
speed in flight, then the bird wouldn't possess feathers at all, only wings!  

Although I am not a physics or aerodynamics expert, I would tend to say that 
feathers definitely are used to help control the bird in flight (this is a 
general thought, or am I mistaken?).  Feathers, like tennis ball fuzz, helps 
the bird glide and land effectively, much like the "spin" shots in tennis.  You 
can do all kinds of things with tennis balls.  A teammate of mine "invented" a 
reverse-spin serve, in which he swiped his racket at a particular speed and 
angle, which made the tennis ball "spin backwards."  He couldn't do this with 
an old tennis ball.  It was impossible, as the absence of fuzz inhibited 
spinning.

To sum up: if the sole purpose of feathers was to help the bird fly faster, 
there would be no feathers.  The bird would probably simply have a wing, and 
evolution may improve and modify that wing to make flying easier, much like 
airplane wings.  Feathers, like tennis ball fuzz, are used for control (for 
steering and landing, and such).  At least that is my take on it...

Arizona by seven.

Steve  

---
***************************************************************
Steve Brusatte-DINO LAND PALEONTOLOGY
SITE: http://www.geocities.com/stegob
ONLINE CLUB: http://clubs.yahoo.com/clubs/thedinolanddinosaurdigsite
WEBRING: http://home.wanadoo.nl/dinodata.net/
INTERNATIONAL LANGUAGE SITE: http://www.geocities.com/stegob/international.html
****************************************************************


Get 250 color business cards for FREE! at Lycos Mail
http://mail.lycos.com/freemail/vistaprint_index.html