Paedomorphism... Fugitive at large

[MariusRomanus@aol.com]

A friend of mine asked me a question once concerning a scenario that was posed 
to him by his first evolutionary biology teacher. He asked me, "If a crime 
takes place and you get 20 people saying it happened one way, but you have 5 
people saying it happened a different way, which of the two stories is most 
likely the correct one?" I replied, "Of course, the story with 20 people 
backing it". With a smile, he responded, "Nope, wrong answer". I was indeed 
shocked and perplexed about this, and started to wonder if my friend had even a 
minimum understanding of statistics. My friend went on to explain that 19 of 
the people saying that the crime had occurred a certain way had all heard their 
story from the 20th person. That person was the single source for their 
collective version of the events. The 5 people telling the other version had 
individually witnessed the event actually taking place. I immediately said, 
"But you didn't tell me that part of it!" to which he responded, "And y!
 ou!
 didn¹t ask".

Many of the different muscles affected by paedomorphism were mentioned in the 
post, *Velociraptor a Mesozoic kiwi? A look at the neoflightless hypothesis* 
(written by???) from the website www.evowiki.org, in such a way as to imply 
that such numerous muscles acted as individual witnesses identifying the perp 
in our crime. The idea that different members of the crown clade of aves had 
lost flight independently of one another was also implied. This in turn was the 
foundation of an argument built with the central tenant that paedomorphism has 
exclusive rights for removing flight in volant animals.
The website also takes the stance that Greg Paul, being the lead proponent for 
the neoflightless nature of avepectorans, does not understand the importance of 
such an idea, stating such things as *However, Paul seems to drastically 
misunderstand the process by which flight is lost in birds.* Personally, I'm 
lead to believe that this is not a true representation of the facts. Though not 
saying that I know this to be certain, but, why not consider the possibility, 
that maybe, Paul simply does not view the selective pressures and end effects 
that go with the loss of flight as being the very same ones experienced by both 
basal dromaeosaurs and the later, more derived aves that ended up giving rise 
to the ratites???

Let's take a closer look at the star witnesses to our crime.

If a bird becomes isolated on an island,, away from predators, its chances for 
survival are good, as long as it can obtain food. If this food can only be 
gathered by utilizing flight, then there is still a selective pressure for 
keeping the ability for flight. If, however, food can be adequately gathered in 
a manner that does not require the ability to fly, then flight could very well 
be lost. The question then becomes one of why; why is flight lost? It's quite 
obvious that the enterprise of flight is an energy-consuming juggernaut. Look 
at it this way: If you have a car that does nothing but sit and look pretty in 
your driveway, but you are still forking out loads of cash for monthly payments 
and for insurance that you don't even need since the car never leaves the 
driveway, then it's quite obvious that you have placed yourself in a huge 
financial disadvantage. Just as you obviously don't need the car you never 
drive, and would be better off without it, sometimes, for speci!
 es!
 that fly, the *need* for flight no longer carries as much weight as it used 
too.

Alan Feduccia has said that paedomorphism could occur in a way that would bring 
about a selective event, resulting in hypertrophied limbs. This implies that 
paedomorphism stimulates these evenst after the fact. But of course, as it is 
with many things that Feduccia has said, this is logic turned on its head.

The chances of paedomorphism invoking selective events at a time in which it 
would be safe to do so, in a way that would not hinder a specie's ability to 
acquire food, escape predation, and successfully mate, boggles the mind.

The paedomorphism that causes flightlessness in modern birds is generally 
believed to be nothing but developmental retardation due to the decreased 
production of thyroxin via the thyroid, and as such it involves little in the 
way of gene modification. Essentially, it's a path of least resistance for 
neoflightless development in animals from the crown clade aves and their more 
immediate ancestors. For what concerns us here, in its very nature, 
paedomorphism is telling you that it is only AFTER the selective pressures
for flight have been lifted can it occur and not be detrimental to the 
organism's survival. In short, if a species no longer needs to rely on flight 
as a mode of survival, and its various needs can be met via other means, 
paedomorphism can now do its thang.

Think about blind salamanders. Only after the salamander was able to carve out 
a niche in a cave was its eyesight selected against. I highly doubt that the 
salamanders first went blind and then thought to themselves, "Woo baby! Look at 
me! I'm blind! I guess now is a good time to go and find a cave." It's simple; 
arresting the development of faculties that are required for an animal's 
survival is not an advantageous thing. It becomes a detrimental handicap 
without traits in place to stand in for it.

It is likely that ratites started to develop terrestrial lifestyles while they 
still had the ability to fly, and as such, they were already selecting for 
hypertrophied limbs before the loss of flight took place. It was only after the 
fully terrestrial skills, physical strength, and other such
elements had developed for effectively acquiring food and escaping danger, 
would the selective pressure for flight disappear. Once this occurred, the 
burden of taking care of those features that were involved in flight became a 
negative selective pressure. Since ratites evolved from animals that had most 
likely lost the ability to gather food or to fight off predators with their 
hands, the attenuation of the limbs would have been no great loss. In fact, it 
would have been beneficial after the fact due to the above-mentioned 
conditions. The energy once used for maintaining flight
mechanics was freed-up and channeled in a manner that utilized it to improve 
their then current viable methods of a fully terrestrial existence.

That's a good scenario for ratites. Unfortunately, what is good for ratites 
isn't good for dromaeosaurs. Life isn't about being in the kitchen baking 
cookies with Martha Stewart. There are no written recipes. There are no cookie 
cutters. Basal dromaeosaurs had forelimbs covered in great big
beautiful asymmetrical feathers. But wouldn¹t ya know it? They still had well 
developed hands. Later dromaeosaurs also had large hands, as well as 
well-developed claws. It is not a stretch of the imagination to see that these 
hands were still being used in the process of defense and/or food acquisition. 
This means that the selective pressures against extensive
paedomorphic activity was still in place (this is not to say that a much more 
subtle amount of peadomorphism could have occurred). Such a thing would be 
absent in the later neornithines that no longer utilized their hands in such 
ways.

It is as Paul has pointed out over and over again... Since basal dromaeosaurs 
were newly volant, their bodies wouldn't have been adapted very far away from a 
flightless style of living. Therefore, they were genetically only a hop and 
skip away from being flightless the entire time.

Kris

http://hometown.aol.com/Saurierlagen/Paleo-Photography.html