Xref: utzoo sci.bio:1949 talk.origins:4668
Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!oliveb!apple!sabol
From: sabol@Apple.COM (Bryan Sabol)
Newsgroups: sci.bio,talk.origins
Subject: Re: The birds and the beaks
Keywords: evolution, birds, beaks
Message-ID: <27761@apple.Apple.COM>
Date: 23 Mar 89 19:01:05 GMT
References: <404@censor.UUCP> <27216@apple.Apple.COM> <464@corpane.UUCP>
Organization: Apple Computer Inc, Cupertino, CA
Lines: 88

In article <464@corpane.UUCP> sparks@corpane.UUCP (John Sparks) writes:
>Your arguement seems to break up for me here. You use the fact that snakes
>and bats don't have front limbs and no beaks, to show that birds did not
>develop beaks just because they don't have front limbs (just wings). What
>does one have to do with the other? Snakes and bats aren't birds. Different
>animals have evolved differently from the same stimuli.

	What I was trying to say is that I don't believe one can
correctly hypothesize that birds developed beaks *solely* because they had
wings/didn't have forelimbs.  While I agree that the absence of
forelimbs may have assisted the development of such a novel item as the
beak, I would say that it would be a secondary developmental pressure at best.  
Much more important to the beak's development was the loss of body mass 
(see the previous article).  So my (albeit extreme) examples of the snakes
and bats was to say that 
1) the absence of limbs (as in the snake) didn't promote beak
development in and of itself, and
2) the ability to fly (such as bats) also doesn't necessitate the
development of a beak.

>If all animals evolved simularly from the same environmental pressures, I could
>use your arguement to ask you then, since bats and some birds both have wings
>and eat the same diet, why don't bats have beaks? 

	This really is an innaccurate statement from the onset.  First,
depending upon the species, birds have an incredibly varied diet. The same goes 
for bats:  there are insect-eating bats, fruit-eating bats, fish-catching bats, 
and, of course, the vampire bats, which subsist on a diet of (mainly) cattle 
blood.  Each different diet reflects modifications in the animal's eating 
apparatus.  
	Next, I definately agree with what you said about similar
evolutionary pressures:  I would say that the reason that bats don't have 
beaks is that they are not birds.  Simple, but true.  The beak was a 
development started by one group of organisms approx. 150 million years ago 
(_archeopteryx_ is generally agreed to be the earliest/best evidence).  A 
very popular evolutionary theory is called "parallel evolution", which means 
that animals with quite different ancestors, but living in the same
environment, will develop along similar lines.  The important idea here
is that though the different animals may look and function similarly,
this doesn't dictate that they will develop the same anatomy/structures.  A
very good example is the shark vs. the killer whale:  very different
animals, with very different apparatae:  one has gills, the other lungs.
One is cold-blooded, the other warm-blooded.  One completed its
evolutionary development roughly 250+ million years ago;  the other is
barely 50+ million years old.

>Don't they [bats] have to save weight? Why do they have teeth? Jaws and 
>such? Why do penguins have beaks? They can't fly. So no need to save weight 
>there. Do penguins have teeth? I believe they do. 

	Yes, to be able to fly, the bat's evolutionary development
required them to lose weight.  Again, according to the parallel
evolutionary theory, the bats didn't *have* to develop beaks;  they
*did* have to find some way of lessening their total mass.  What I'm
trying to say is that the beak was a great development which lessened
the total mass of an animal -- but it isn't/wasn't the *only* way to
lose mass.  The bat is such an example.
	I don't know why bats retained all the teeth/jaw apparatus and
still are able to fly.  I'd be interested to hear of ideas.  One guess
is that they lessened the total mass of their jaws as much as possible,
and they also may have a much lower glide ratio than the average flying
bird.
	No, penguins do not have teeth.  They do have serrated edges
along their beaks, but no teeth.  If you look at the skeletal structure
of a penguin, you'd be amazed at their mass.  They have, as a
genus/species, been "grounded" for millions of years, which has enabled
them to develop more along the lines of a seal/dolphin/etc. than what
one would normally consider a bird.  
	Penguins still have beaks because they come from the same ancestory 
as all birds.  As I mentioned before, the beak is a very useful tool, and 
the penguins have adapted it to their marine feeding techniques.  Think of 
it this way:  it's much easier for an animal to adapt an existing structure 
than it is to develop a totally new one.  The beak was a new type of structure,
and this is one of the reasons why I believe it hasn't appeared in any other
life form:  it's quite unique.  So, penguins have retained their beaks
since it's easier to modify what they already have (i.e., a beak) than
it would be for them to lose a beak and once again develop teeth/jaws.
Ergo, we see a thick, heavy bill, with sharp serrations along the edges.
Just right for catching fish/squid.

>What is the air speed velocity of a swallow?

	What do you mean?  European or African?

bryan sabol
ousted reedie-at-large