Evolution?

Try the Bible/Torah/Qu''ran/other holy book; they contain all of the answers.

Just so you know, this will end up a war between religion and science. It always does. No disclaimer at the end of a post is going to change that.

---

"Yes, ''n'' how many ears must one man have
Before he can hear people cry?
Yes, ''n'' how many deaths will it take till he knows
That too many people have died?
The answer, my friend, is blowin'' in the wind,
The answer is blowin'' in the wind." -- Bob Dylan

Click

quote:

---

Original post by Subconscious
Please no religious answers, I want a logical discussion about theories of evolution.

---

What he said.

quote:

---

Original post by Subconscious
Try the Bible/Torah/Qu''ran/other holy book; they contain all of the answers.

---

No trolling. Answer him; I want to know too.

---

Jesus saves ... the rest of you take damage.
"A page of history is worth a volume of logic." -- Oliver Wendell Holmes

quote:

---

Original post by Subconscious
That all makes sense to me, but there is something that doesn''t really make sense. How can major changes be developed through evolution, if there is no immediate benifet from them? For example, how can something evolve to have wings?

---

Wings are an interesting and puzzling example. With something like the eye, it''s become accepted that a complicated eye structure can be developed very rapidly and even the most primitive eye creates a major advantage.

Flight has developed independently in different creatures at different times in history. Insects had it first -- probably before there were any land reptiles, then gliding reptiles appeared, then large pterosaurs, then birds, then winged mammals.

The membrane necessary for gliding isn''t particularly intrusive and it doesn''t take much to give the animal an advantage. It''s easy to see how gliders evolved quickly. Powered flight and large gliders are different. I''m not too familiar with the mechanics of flight, but perhaps early non-functional wings provided some advantages in running or jumping? Ever observed a bird with its wings clipped? They can still hop around and break their falls with their wings.

quote:

---

Of course I can see how a species would lose its wings and ability to fly. If the ability to fly is no longer advantageous and the wings get in the way, the species may slowly lose its wings, but gaining wings is a completely different story.

---

Wings may have only had a chance to develop fully in creatures which already had a significant advantage in leg strength, for instance. Perhaps the wings then did nothing to hinder it even if they were useless -- the animals may have no longer needed forearms. Look at the Tyrannosaurus, for instance. It''s forearms were essentially useless yet this was common in a wide variety of large predators of the era.

quote:

---

The same kind of problem also goes for things like gaining lungs or gills, they would be useless until completely functional and random mutations can not form something so complex in just one generation.

---

Here your assuming that partially developed lungs or gills would not be functional. Organisms have always had to absorb chemicals from their surrounding environment so its entirely possible that lungs developed gradually over time to become increasingly more functional. Bad mutations would have been more likely to kill the organism and therefore only good mutations could survive.



----
Bart

quote:

---

The membrane necessary for gliding isn''t particularly intrusive and it doesn''t take much to give the animal an advantage. It''s easy to see how gliders evolved quickly. Powered flight and large gliders are different. I''m not too familiar with the mechanics of flight, but perhaps early non-functional wings provided some advantages in running or jumping? Ever observed a bird with its wings clipped? They can still hop around and break their falls with their wings.

---

That assumes that the route taken was a treetop based one, i.e. reptiles gliding down from tops of trees, and not a land based one, which there appears to be a controversy over in the link I posted. To be honest, the explanation in the isn''t really helpful, they note that the earliest winged creatures had fully developed feathers yet were flightless. It then lists why feathers could have developed, but gives no reason as to why we don''t see creatures other than birds with feathers (does the platypus have them, that''s a bit of an exception), which to my mind at least, implies that their evolutionary advantage was associated with flight.

I''ll ask this question on StraightDope, and see whether a paleantologist can answer it.

quote:

---

Original post by MDI
That assumes that the route taken was a treetop based one, i.e. reptiles gliding down from tops of trees, and not a land based one, which there appears to be a controversy over in the link I posted. To be honest, the explanation in the isn''t really helpful, they note that the earliest winged creatures had fully developed feathers yet were flightless.

---

This controversy is about powered flight, specifically about birds. Small gliding reptiles existed over a hundred million years before birds -- think gliding lizards.

I remembered reading an article about an experiment that shed some new light on this and a Google search turned up this:

quote:

---

Learning to fly.

The New York Times yesterday described an interesting and serendipitous discovery about juvenile birds' use of their wings, which has potential implications for how winged flight evolved:
The behavior of chukar partridge chicks, which can run straight up the side of a hay bale or a tree while flapping their wings, may offer a new window on the origin of flight in birds.

Feathered dinosaurs may have done something similar, Dr. Kenneth P. Dial of the University of Montana suggests in today's issue of Science. He suggests that they too flapped their primitive wings to help them climb, which brought them off the ground and closer to discovering the aerial possibilities of their wings. Even incompletely feathered proto-wings, Dr. Dial says, would have been useful in running up inclines.

One of Dr. Dial's findings, which has surprised other scientists who study the evolution of flight, is that the chukar chicks did not use their wings to raise them off the ground. The wing beats served the same purpose as spoilers on race cars. The force generated by flapping pressed the chicks into the surface on which they were running for better traction. As Dr. Dial said of his finding, "It's not intuitive."

In fact, he came upon the behavior accidentally. His teenage son, Terry, was helping him study the development of flight in chukar chicks. While Dr. Dial was traveling, his son was keeping track of the young birds as their feathers grew, and they gradually launched themselves on longer flights, horizontally and vertically.

The vertical flights used hay bales as an obstacle. When Dr. Dial returned from a trip, he said, his son told him the chicks were not staying with the program. "They're cheating," Dr. Dial recalled his son telling him, "They're not flying anymore. They're running up."
Dial videotaped the chicks using their immature wings to run up vertical and near-vertical inclines, and the movies are on the website of the journal Science, where his report is published. Unfortunately, you need a subscription to get in, so I searched around and found his own homepage, which has those videos and more. He has them in AVI format; some of them are also on a National Science Foundation site in other formats. They must be seen to be believed -- not only cool, but adorable. Go, li'l birdie, go!

---

[edited by - mattnewport on April 17, 2004 3:15:14 PM]

As far as flight goes it''s just like what is posted above. Just because an animal doesn''t have fully developed wings that doesn''t mean that they are a hindrance. Remember, if evolution is true it didn''t work with wings in mind, they are just the logical result of what was happening with that animal. Think of the "flying" (gliding) squirrel. It can''t actually fly, but it can glide pretty far because of its flaps, or whatever they are called. As time goes by squirrels that have larger flaps and can glide the farthest will be better suited and live, if they are very lucky one day Santa will pay them a visit and teach them to flap their flaps and fly.

With evolution keep something in mind, we are still learning. Not too long ago some scientists found that DNA had the ability to store mutations for generations without them becoming apparent, with them only showing when the environment becomes too hostile for most of that species to survive. In this way a species as a whole can store millions of possible mutations then when something happens that triggers it all of them happen at once and only the good ones survive long enough to reproduce. There is an article about it somewhere on newscientist.com, but I''m too lazy to track it down.

---

"The paths of glory lead but to the grave." - Thomas Gray
I kick ass, my URL says so.
My Online Photo Gallery

quote:

---

Original post by trzy

quote:

---

The same kind of problem also goes for things like gaining lungs or gills, they would be useless until completely functional and random mutations can not form something so complex in just one generation.

---

Here your assuming that partially developed lungs or gills would not be functional. Organisms have always had to absorb chemicals from their surrounding environment so its entirely possible that lungs developed gradually over time to become increasingly more functional. Bad mutations would have been more likely to kill the organism and therefore only good mutations could survive.

---

Yes, organisms always had to absorb chemicals from their surrounding environment, but absorbing oxygen from water and absorbing it from air, require quite different functioning organs. I don''t believe that for a species evolved to live in the water, being able to absorb a little bit of oxygen from air instead of water would be particularly helpful. It would have to be able to absorb enough to sustain itself for some amount of time outside the water to have any advantage, and it seems like that would be too big of a jump to make in one generation.

quote:

---

Original post by Subconscious
Yes, organisms always had to absorb chemicals from their surrounding environment, but absorbing oxygen from water and absorbing it from air, require quite different functioning organs. I don''t believe that for a species evolved to live in the water, being able to absorb a little bit of oxygen from air instead of water would be particularly helpful. It would have to be able to absorb enough to sustain itself for some amount of time outside the water to have any advantage, and it seems like that would be too big of a jump to make in one generation.

---

There are fish that can survive out of water for extended periods of time by keeping their gills moist. Perhaps the earliest amphibians still retained gills -- being able to venture onto land where there was no competition for food for even very short periods of time would have been tremendously advantageous.

Is it out of the realm of possibility for an organism to have a hybrid lung/gill system?




----
Bart

lungfish

quote:

---

That all makes sense to me, but there is something that doesn''t really make sense. How can major changes be developed through evolution, if there is no immediate benifet from them?

---

Sexual behaviour. If some species considers some quality as sexy, that quality will become more and more prevalent even if it doesn''t improve survival rate. Basically, species _can_ and _do_ design themselves. Memes affecting genes - cool stuff.

quote:

---

Original post by Subconscious
How can major changes be developed through evolution, if there is no immediate benifet from them? For example, how can something evolve to have wings? No amount of random genetic mutations or variations will allow one of the species to suddenly have wings and be able to fly, it would have to be a gradual change. But when wings first start to develop they would be completely useless and offer no reproductive advantage, in fact the deformed, partially winged, member of the species would probalby be easier prey if anything.

---

Yours is one of the most interesting questions I've heared in a long while.

I'm not an expert about evolution, but I've a great imagination and I already came up with an explanation for the wings thing:

I bet they were developed by little dinosaurs who's better hability was to jump. Maybe after a couple of millons of years after jumping and waving their little arms they became wings.

Look at this draw of an archaeopteryx:


Long (maybe musculated) legs, long arms (long like if they needed to reach something high).

Maybe this little dinosaurs lived in the top of trees and used their arms to balance while jumping from one to another.


[edited by - owl on April 17, 2004 7:23:19 PM]

In the case of lungs and gills, oxygen needs to diffuse throughout the organism for metabolism. Diffusion works over a certain surface area. If a circulatory system is present, then it becomes more advantageous for an organism increase the surface area to volume ratio of its exposed region. The simplest way to do this is a depression. The deeper this depression goes, the greater the surface area to volume ratio; this is the evolutionary advatange. If you have a large depression, dimpling it with smaller depressions further increases the surface area. The problem with depressions is that the air/water in them tends to lose its oxygen (become "stale"). So an organism in which the depression goes all the way to the other side (the same principle as digestive systems) or expels the air (as in lungs) becomes an evolutionary advantage. But if you''ve got a cavity that goes all the way through, the fluid that gets in the dimples will become stale, so it''s probably a better idea for these things to be pretty smooth.

Now, if you''re close to land and occasionally get beached because you''re feasting on the bacteria near land when the tide rolls out and you''ve got lungs, you can expel the stale water and breathe fresh air. Air has much lighter weight than water, so if you breathe more rapidly and weakly you can get the same amount of oxygen you got while you were in the water. Not so with gills. The movement of air is much weaker than water, and you don''t have any facilities to walk on land yet, so you''ll end up getting a tiny fraction of the oxygen you got while in the water.

As for flight, feathers developed first (they insulate better than scales). Then the flight stroke developed. I saw something on the evolution of flight and it suggested that a certain kind of feathered dinosaur used what would become the flight stroke when it pounced on its prey. I guess the advantage would then be the distance from which it could pounce or the speed thereof. Reptiles with feathers don''t exist because of the same reason why dinosaurs don''t exist -- sudden climate change killed all the large coldblooded creatures.

Link

A very interesting article on the development of flight which cites James Mardens research on stone-fly evolution.

quote:

---

I bet they were developed by little dinosaurs who''s better hability was to jump. Maybe after a couple of millons of years after jumping and waving their little arms they became wings.

---

You''re saying that the memories of excessive jumping is passed on through hundreds of generations?

Well... the less effective jumpers would have been removed from the gene pool for obvious reasons. (If this actually happened.)

quote:

---

Original post by Katta

quote:

---

I bet they were developed by little dinosaurs who''s better hability was to jump. Maybe after a couple of millons of years after jumping and waving their little arms they became wings.

---

You''re saying that the memories of excessive jumping is passed on through hundreds of generations?

---

Obviously. Instinctive behavior is a well documented phenomenom.

CM

quote:

---

Original post by Conner McCloud

quote:

---

Original post by Katta

quote:

---

I bet they were developed by little dinosaurs who''s better hability was to jump. Maybe after a couple of millons of years after jumping and waving their little arms they became wings.

---

You''re saying that the memories of excessive jumping is passed on through hundreds of generations?

---

Obviously. Instinctive behavior is a well documented phenomenom.

CM

---

The problem with this idea is that physical behaviour of an organism has very little impact on the genetic makeup of an animal and baring exposure to some form of material that would force a radical alteration in the genetic structure, this kind of genetic propagation of an attribute.

The "memory" of excessive jumping is passed on through "social behaviour" of organisms. Over time the social evolution of an organism weeds out the least likely or able to conform to that social requirement. Therefore the social behaviour supports the underlying "greedy genes" which only propagate the information needed to ensure the further survival and expression of the genes of the organism.

This sort of multi-generational "social behavior" also accounts for the shift from single celled organisms to multicellular organisms and eventually complex organisms. The specialization experienced through symbiosis causes the organisms which are most able to provide certain behaviour. As these cells reproduce in simple environments they would be merged into an environment where they must compete with others of the same behaviour to survive. The cells which make up circulatory systems of primitive multicellular organisms are those organisms which are best able to withstand the pressure and abuse of moving quickly, and also able to properly exchange and withstand toxins in the circulatory system.

It is important to note that while specialization and therefore the instinctive ability to use those specializations is genetic, "memory" (in the context of learned behaviour) itself is not.