[_ Old Earth _] Do Birds' Lungs Throttle Evolution?

[Asyncritus]

Introduction

Since no explanations (or evidence) is forthcoming that beneficial mutations could produce the 6,000,000 or so existing species, plus the several million extinct ones, then perhaps we could profitably consider some other lines of non-genetic evidence which equally powerfully destroy the theory right down to its socks.

BIRDS’ LUNGS

As Darwin said, “If it could be demonstrated that any complex organ existed which could not possibly have been formed by numerous, successive slight modifications, my theory would absolutely break down”

Here’s a prize example which pulverises it completely.

One of the very biggest stumbling blocks to the theory of evolution by gradual steps or in mighty leaps, is that group of magnificent creatures, the birds.

The theory at present, holds that the birds evolved from the reptiles. That the scales of reptiles somehow became frayed out and turned into feathers over millions and millions of years.

Look carefully at the scales on this snake.

http://www.oceanlight.com/thumbs/12585.jpg

Here’s a flight feather:

http://www.afsc.noaa.gov/Quarterly/amj2005/images/feather.jpg

I’m sure you can see some of the visible problems involved in producing the flight feather from the scale. (Incidentally, there are about 10 DIFFERENT TYPES OF FEATHER on the same bird! All that from one scale? What nonsense.]

When we look at the detailed structure of the feather, the problems become astronomical, and the evolution proposal absurd.

That somehow, a torpid, cold-blooded reptile turned into the warm-blooded bird with probably the highest metabolic rate in the animal kingdom.

(In case the pedants are out in force, I am referring to the ectothermic and endothermic animals. Ectotherms have variable body temperatures, endotherms have constant body temperatures).

Whatever problems evolving that lot involved, they pale into insignificance in the presence of the one fact which I shall now describe. It is the difference between the lung of a reptile, and the lung of a bird.

 

[Asyncritus]

Re: Do Birds' Lungs Throttle Evolution? Part 2

To crudely illustrate the problems that the evolutionist has to account for, think of an ordinary balloon and air entering and leaving that balloon.

It enters the neck, goes into the balloon, and is squeezed out. BOTH INFLOW AND OUTFLOW USE THE SAME NECK. So air that is going to go out of the balloon, can mix with the air that’s just coming in. There is TWO WAY airflow.

That’s a reptile’s lung, very similar to ours. There’s a MIXTURE of incoming and outgoing air in our lungs.

Now think of one of those long, thin balloons, like the ones used at parties to make dogs and so forth, with a hole AT BOTH ENDS.

Bend it into a U shape, and blow into one end.

Air goes in at one end, and out the other, rather like a jet engine or a wind tunnel.

That’s how the bird’s lung works. IT USES ONE WAY TRAFFIC. There is NO MIXING of incoming and outgoing air.

How does the first sort of lung (in the reptile) become the second kind (in the bird)?

No evolutionary explanation for that fact is possible, and to hypothesise dinosaurs with feathers running round and turning into birds is a complete nonsense. Their lungs say so. As Michael Denton says:

“Just how such an utterly different respiratory system could have evolved gradually from the standard vertebrate design is fantastically difficult to envisage, [Asy: I think he's trying to avoid the words 'impossible to envisage'] especially bearing in mind that the maintenance of respiratory function is absolutely vital to the life of an organism to the extent that the slightest malfunction leads to death within minutes.”

So imagine a reptile whose lungs developed a big hole in the bottom for the air to flow through. Guess what? Yeah.

 

[Asyncritus]

“Just as the feather cannot function as an organ of flight until the hooks and barbules are coadapted to fit together perfectly, so the avian lung cannot function as an organ of respiration until the parabronchi system which permeates it and the air sac system guarantees the parabronchi their air supply are both highly developed and able to function together in a perfectly integrated manner.”

Those are the headlines. Here is some more detail so any interested parties can examine them and satisfy themselves that the above description is correct. Follow the blue arrows in the inhalation diagram (the top one) and the exhalation diagram (below) to see that there is no mixing of incoming and outgoing air.

INHALATION

EXHALATION

http://people.eku.edu/ritchisong/RITCHISO/Airflowrespiration2.gif

“So, it takes two respiratory cycles to move one 'packet' of air completely through the avian respiratory system (see 1, 2, 3, & 4 above). The advantage, though, is that air, high in oxygen content, always moves unidirectionally through the lungs.”

Here is a more pictorial representation of inhalation:

http://www.darwinismrefuted.com/res/95a.jpg

and exhalation:

http://www.darwinismrefuted.com/res/95b.jpg

 

[Asyncritus]

The system is described as a counter-current/flow system, where air with the highest concentration of oxygen meets blood with the lowest concentration of oxygen across the membranes.

It is an extremely efficient system, used by intelligent design engineers to maximize heat exchange or other. “In counter-flow heat exchangers the fluids enter the exchanger from opposite ends. The counter current design is most efficient, in that it can transfer the most heat.” Wiki.

Now you’ve looked at those facts, consider how the one system could have evolved from the other.

Denker also raises the interesting point that “the avian lung cannot be inflated out of a collapsed state as happens in all other vertebrates after birth. … the air capillaries are never collapsed as are the alveoli of other vertebrate species; rather as they grow into lung tissue, the parabronchi are from the beginning open tubes filled either with air or fluid (which is later absorbed into the blood capillaries).”

This set of facts alone finishes any idea that a bird evolved from anything. This kind of breathing occurs nowhere else in the vertebrates. It has no ‘common ancestors’.

Therefore birds are a completely unique creation, and did not ‘evolve’ from anything else.

 

[Asyncritus]

Nice summary here: http://www.science.org.au/nova/newscientist/104ns_002.htm

“When a bird breathes in, air does not go directly into the lungs. Instead, it enters the air sacs, where it is stored briefly before passing into the lungs at the next inhalation.

In this way, air enters and exits a bird's lungs at different points - in via the air sacs, out via the windpipe - allowing them to maintain near-constant, one-way airflow through their lungs.

This allows a countercurrent system to be set up between the air and the bloodstream, with air passing in one direction and blood in the other. The result is far more efficient gas exchange between air and blood than is possible in lizards, or even mammals.

The differences between animals that use air sacs and those that don't are striking.

Birds extract more oxygen from the air than any other animal of comparable size. At sea level they are 33 per cent more efficient at extracting oxygen than mammals.

At 1500 metres a bird may be 200 per cent more efficient. This gives birds a huge advantage over mammals at altitude. It also explains why geese can migrate over the Himalayas at an altitude that would kill a human.”

Asyncritus

 

[Barbarian]

The first thing to note is that other vertebrates also have a flow-through ventilation system. In the alveoli, there are small openings called the Pores of Kohn, by which one alveolus communicates with another. When there is bronchial obstruction, this functions as a ventilation pathway known as "collateral ventilation." It isn't very good, but it does work. In birds, this has become the primary pathway; the bird lung is essentially a very large alveolus, and the collateral ventilation is now the primary form.

And in birds, it's become very efficient, indeed. But structurally, it's a modification of the primitive vertebrate form. BTW, many theropod dinosaurs had hollow bones with sacs from the lungs. Some mammals have simlar evaginations of the lungs, including some humans. It's just much greater in extent in birds.

Would you like to learn some details?

And now there's this:
Some hollow bones are providing solid new evidence of how birds evolved from dinosaurs. Scientists have discovered a new carnivorous dinosaur that breathed like a bird...“What was really key was some of the bones around the rib cage of the animal, bones that only in birds are invaded by air sacs from the lungs,” says Sereno. “Having found these air pockets in Aerosteon, we reasoned that we really have to accept that Aerosteon and other predatory dinosaurs, likely feathered, these dinosaurs likely breathed like birds.”
http://www.sciencentral.com/video/2009/03/25/dinosaur-bird-bones/

 

[Asyncritus]

The first thing to note is that other vertebrates also have a flow-through ventilation system. In the alveoli, there are small openings called the Pores of Kohn, by which one alveolus communicates with another. When there is bronchial obstruction, this functions as a ventilation pathway known as "collateral ventilation." It isn't very good, but it does work. In birds, this has become the primary pathway; the bird lung is essentially a very large alveolus, and the collateral ventilation is now the primary form.

And in birds, it's become very efficient, indeed. But structurally, it's a modification of the primitive vertebrate form.

Would you like to learn some details?

I think the 'pores of Kohn' are a pretty pore piece of nonsense in this context.

Do you know what an alveolus really is?

And how 'pores' connecting alveoli, relate to inflow and outflow of air from whole lungs?

A pretty pore show Barbarian, which fails to answer any serious questions once again.

Care to account for how a reptile lung can become a bird lung? Or have you got another leaking theory?

 

[Asyncritus]

And now there's this:
Some hollow bones are providing solid new evidence of how birds evolved from dinosaurs. Scientists have discovered a new carnivorous dinosaur that breathed like a bird...“What was really key was some of the bones around the rib cage of the animal, bones that only in birds are invaded by air sacs from the lungs,†says Sereno. “Having found these air pockets in Aerosteon, we reasoned that we really have to accept that Aerosteon and other predatory dinosaurs, likely feathered, these dinosaurs likely breathed like birds.â€
Dinosaur Bird Bones | ScienCentral | Science Videos | Science News

Don't these jokers ever think about what they're saying? And do you ever think about what they're saying? Or just cut and paste a likely-looking quote hoping nobody will read them?

Air sacs from the lungs do not allow air to escape from the lung, BUT THE AIR HAS TO EXIT VIA THE SAME WAY IT ENTERED THE LUNGS.

Tough luck pal.

Do remember that we are attempting to explain how a balloon-type lung with TWO-WAY air flow, could evolve into a wind-tunnel type lung with ONE WAY air flow.

 

[Deavonreye]

Though interesting, just because there may not be a current explaination [and I'm not saying that no one in the science community HASN'T explained this], does NOT automatically make "divine creation" the only other answer. But thank you for the quick look at avian respiratory physiology.

 

[jasoncran]

i wonder if the community of science will ever admit the answers to origins isnt completely answerable. we cant know it as it requires things outside the limits of science.

i prefer if my money is to be wasted let cures for diseases to be found not sophisicated guesswork on origins on both sides of the debate.

 

[Deavonreye]

i wonder if the community of science will ever admit the answers to origins isnt completely answerable. we cant know it as it requires things outside the limits of science.

i prefer if my money is to be wasted let cures for diseases to be found not sophisicated guesswork on origins on both sides of the debate.

I agree that most grant money should be spent on ways to better the species.

However, I don't believe that we [humans] should ever stop looking for answers. What we may not know now, we may in the future. What was once thought to be "barriers" were eventually overcome. For me, it matters little if they do or do not find those answers. Attempting to, however, IS important.

 

[lordkalvan]

I think the 'pores of Kohn' are a pretty pore piece of nonsense in this context.

Do you know what an alveolus really is?

And how 'pores' connecting alveoli, relate to inflow and outflow of air from whole lungs?

A pretty pore show Barbarian, which fails to answer any serious questions once again.

Care to account for how a reptile lung can become a bird lung? Or have you got another leaking theory?

More personal incredulity from Asyncritus masquerading as critical comment while refutations of his arguments and unanswered points elsewhere remain ignored. It figures.

 

[Barbarian]

I think the 'pores of Kohn' are a pretty pore piece of nonsense in this context.

I can understand the frustration. You were told that a single-directional ventilation was unique to birds, and it's present in humans in the form of collateral ventilation via the pores of Kohn.

Do you know what an alveolus really is?

I had to get through comparative anatomy, histology, and physiology. Yep. I know what they are.

And how 'pores' connecting alveoli, relate to inflow and outflow of air from whole lungs?

The avian lung is topologically like a single alveolus, with greatly increased collateral ventilation.

A pretty pore show Barbarian, which fails to answer any serious questions once again.

As you see, birds have a form of ventilation that is only secondary in other tetrapods, but has evolved to be the primary form in that class. Not surprising.

Care to account for how a reptile lung can become a bird lung?

It's not hard to see. First, collateral ventilation becomes easier with the connections between alveoli enlarged. The necessity of this coming about in the advanced theropod dinosaurs is clear; reptiles generally breath by expanding and contracting ribs (this is a third method in mammals, which is why cracked ribs hurt when you laugh). But the small dromaeosaurs were actively grabbing prey and even gliding on feathered limbs, which meant the pump muscles were being used for other things. This occured at the same time we see lung sacs in those dinosaurs. So the pumping function could be transferred to the sacs.

Once the collateral ventilation is established, the simplification of the lungs is possible by reducing the numerous alveoli to fewer air sacs, and by evolving one-way valves that increase the efficiency of the system.

This is just one of many ways it could have happened. It has the virtue of being consistent with the evidence from fossils.

 

[Deavonreye]

Very interesting post, Barbarian. Well thought out and delivered.

 

[Asyncritus]

I can understand the frustration. You were told that a single-directional ventilation was unique to birds, and it's present in humans in the form of collateral ventilation via the pores of Kohn.

I don't know quite what you learnt in the courses you mentioned, B.

Here's wiki: The Pores of Kohn are pores between adjacent alveoli, or interalveolar connections. They function as a means of collateral ventilation; that is, if the lung is partially deflated, ventilation can occur to some extent through these pores.

Don't you know what that means? It's quite simple, really.

In all OTHER lung breathers, air enters nares, tracheae, bronchi, alveoli and out again in reverse.

From alveolus to alveolus via pores of Kohn does not help one little bit - because from the alveoli it returns on the way out via bronchi trachea etc.

At no time does it escape into the body cavity, and then out via the nares.

In the birds, please note again, there is ONE WAY traffic. The inhaled air NEVER PASSES OUT THE WAY IT ENTERED, until it returns to the trachea.

To put it even more simply, in the birds, AIR ENTERS THE LUNG ON THE EXHALATION CYCLE.

In reptiles and ALL OTHER ANIMALS WITH LUNGS, air enters the lungs on INHALATION.

Try explaining that fact. LK can say what he likes about personal incredulity, but until he can produce even the vestige of an EVOLUTIONARY explanation of these FACTS, then the case is dead in the water.

Birds are one of the largest groups of animals extant - and here is a simple fact which evolution cannot account for.

When are you guys going to recognise it for what it is, i.e. useless at explaining any concrete facts? And give it up?

I had to get through comparative anatomy, histology, and physiology. Yep. I know what they are.

If they didn't tell you that alveoli do NOT convey air out of the lung into the body cavity, then it was a pretty poor course.

If they didn't tell you that air sacs don't convey air out of the lungs either, then again the course content was a little dubious.

The avian lung is topologically like a single alveolus, with greatly increased collateral ventilation.

Where do you get this nonsense?

Didn't they tell you that a lung is made up of a HUGE NUMBER of alveoli? But a bird's lung DOES NOT HAVE ALVEOLI.

Here's a nice diagram of the differences between birds lungs and all others.

How can you possibly regard a bird lung as an alveolus gone mad? It wasn't the alveolus that went mad.

As you see, birds have a form of ventilation that is only secondary in other tetrapods, but has evolved to be the primary form in that class. Not surprising.

It would be most surprising if that did happen.

Somewhere, somehow, a reptile 'evolved' a great hole in the bottom of its lung. Somewhere, somehow, it 'evolved' a connection between the hole at the bottom of the lung and the nares.

Somehow, somewhere, the trachea became disconnected from the lung and got hooked up to the air sacs.

The air sacs somewhere, somehow, once upon a time, sent air into the lungs via the parabronchial system.

Somewhere, sometime, birds (or was it reptiles?) forgot that their lungs and chest have to expand and contract on inhalation and exhalation:

Bird lungs do not expand or contract like the lungs of mammals. In mammalian lungs, the exchange of oxygen and carbon dioxide occurs in microscopic sacs in the lungs, called 'alveoli.'

In the avian lung, the gas exchange occurs in the walls of microscopic tubules, called 'air capillaries.'

http://www.edb.utexas.edu/petrosino/Legacy_Cycle/mf_jm/Challenge3/Pet Educatio-Birds.pdf

Somewhere, somehow, the reptile decided it would abandon alveoli in favour of the parabronchi, which as you can see from the above, are a system of tubules. So much for your 'large alveolus' concept!!!

It's not hard to see.

You're right. It isn't. It's impossible.

First, collateral ventilation becomes easier with the connections between alveoli enlarged. [...]

Unfortunately for you, somewhere, somehow, the reptiles had to forget to expand and contract their chests.

Then they thought, Hey, it'd be a good idea to lose our diaphragms as well, so we can become birds.

Once the collateral ventilation is established, the simplification of the lungs is possible by reducing the numerous alveoli to fewer air sacs, and by evolving one-way valves that increase the efficiency of the system.

Once more with feeling. Birds DO NOT HAVE ALVEOLI where air is exchanged.

They have parabronchial tubules instead.

This is just one of many ways it could have happened. It has the virtue of being consistent with the evidence from fossils.

In view of the above, don't you think it would be a good idea to give up at this point? :

PS

Here's Ruben on the subject:

"Recently, conventional wisdom has held that birds are direct descendants of theropod dinosaurs.

However, the apparently steadfast maintenance of hepatic-piston diaphragmatic lung ventilation in theropods throughout the Mesozoic poses fundamental problems for such a relationship.

The earliest stages in the derivation of the avian abdominal air sac system from a diaphragm-ventilating ancestor would have necessitated selection for a diaphragmatic hernia in taxa transitional between theropods and birds.

Such a debilitating condition would have immediately compromised the entire pulmonary ventilatory apparatus and seems unlikely to have been of any selective advantage."

That's putting it mildly, isn't it?

 

[jasoncran]

I agree that most grant money should be spent on ways to better the species.

However, I don't believe that we [humans] should ever stop looking for answers. What we may not know now, we may in the future. What was once thought to be "barriers" were eventually overcome. For me, it matters little if they do or do not find those answers. Attempting to, however, IS important.

do so at the markets expense not taxpayers.

we cant afford nasa. best to let the military use rockets for what we really do get from nasa.

useable weapons tech, you laugh? we are communicating via that. and you all use the gps systems if you have them.

nasa is only a third of what is on the cape. nasa goes the cape still functions. its kinda interested me when i learnt of that.

 

[Rhea]

Asyncritus, you damage your own argument when you use such phrases as

Somewhere, somehow, the reptile decided it would abandon alveoli in favour of the parabronchi,

The reader is forced to wonder

1. whether it is a deliberate straw-man, and you are well aware that evolution never (ever) depends upon an organism "deciding" on a change, but you want to pretend that was Barbarian's argument (when it never was) and knock down that false argument; or
2. whether you are actually unaware of the fact that evolution never (ever) depends upon an organism "deciding" on a change.

You've used such phrases quite a bit in your rebuttals, and the audiance is anxious to know - is the answer 1 or 2?

 

[Barbarian]

I don't know quite what you learnt in the courses you mentioned, B.

Some of the things you weren't aware of regarding the structure of bird lungs, for example.

The Pores of Kohn are pores between adjacent alveoli, or interalveolar connections. They function as a means of collateral ventilation; that is, if the lung is partially deflated, ventilation can occur to some extent through these pores.

Don't you know what that means?

It means that it functions as a secondary airway. The air goes down into the alveolus, through the pores of Kohn, and back out another bronchus via another alveolus.

In all OTHER lung breathers, air enters nares, tracheae, bronchi, alveoli and out again in reverse.

No. It's a one-way trip, unlike the usual, in which the air goes down into an avleolus and the back out the way it came in.

At no time does it escape into the body cavity, and then out via the nares.

Bird lungs don't release air into the body cavity, either. The one-way path of collateral ventilation is refined and improved in birds to become the primary form.

In the birds, please note again, there is ONE WAY traffic. The inhaled air NEVER PASSES OUT THE WAY IT ENTERED, until it returns to the trachea.

That's what collateral ventilation is.

To put it even more simply, in the birds, AIR ENTERS THE LUNG ON THE EXHALATION CYCLE.

Try explaining that fact.

As you learned, that's what happens in collateral ventilation. The exhalation of air through the pores of Kohn, into another avleolus and out the trachae, also pulls new air into the alveolus.

That's how it works.

LK can say what he likes about personal incredulity, but until he can produce even the vestige of an EVOLUTIONARY explanation of these FACTS, then the case is dead in the water.

As you learned, it's quite easy to see how very simple changes could produce the highly refined form of collateral ventilation we see in birds.

Barbarian observes:
I had to get through comparative anatomy, histology, and physiology. Yep. I know what they are.

If they didn't tell you that alveoli do NOT convey air out of the lung into the body cavity, then it was a pretty poor course.

Unless you're injured and in big trouble, air never goes from the lung into the body cavity. That prevents breathing entirely.

If they didn't tell you that air sacs don't convey air out of the lungs either, then again the course content was a little dubious.

The evidence is that they did so in dinosaurs, and of course, they do so in birds. Did you look closely at the diagram you posted?

Barbarian observes:
The avian lung is topologically like a single alveolus, with greatly increased collateral ventilation.[/QUOTE]

Where do you get this nonsense?

You've been gulled into believing that there is no way for this to appear over time. But...

Archosaur and theropod lungs are hypothetical constructs. Extinct groups are marked with a "+", and perforations between chambers are marked with "*." Perry proposes that these perforations play a crucial role in the stepwise evolution of the avian parabronchi, as indicated in the detail sketches of theropod and avian-grade lungs. CrC and CaC are cranial [forward part of the trunk] and caudal [rearward part of the trunk] chambers, which are connected with the respective regions of the intrapulmonary bronchus. MvB and MdB are avian medioventral bronchi and mediodorsal bronchi, which are proposed to evolve from CrC and CaC, respectively, as indicated by small arrows.

From Figure 6, p. 161 of: Perry, Steven F. (1992). "Gas exchange strategies in reptiles and the origin of the avian lung". Physiological Adaptations in Vertebrates. Wood, S. C., Weber, R. E., Hargens, A. R. and Millard, R. W., Eds. New York, Marcel Dekker: 149–167.


So there's no reason why this can't evolve. It's one of the simpler sorts of change we see in evolution.

Barbarian observes:
As you see, birds have a form of ventilation that is only secondary in other tetrapods, but has evolved to be the primary form in that class. Not surprising.
It would be most surprising if that did happen.

Somewhere, somehow, a reptile 'evolved' a great hole in the bottom of its lung. Somewhere, somehow, it 'evolved' a connection between the hole at the bottom of the lung and the nares.

No. As you see, it was more gradual than that.

Somewhere, somehow, the reptile decided it would abandon alveoli in favour of the parabronchi, which as you can see from the above, are a system of tubules. So much for your 'large alveolus' concept!!!

Someone's already taken you to task for that error, but I'll just point out again, that the change obviously can happen gradually over time. Indeed, as you learned, the first elements were already in place in the advanced dinosaurs, and the first birds didn't have a completely avian lung.

Barbarian observes:
First, collateral ventilation becomes easier with the connections between alveoli enlarged.

Unfortunately for you, somewhere, somehow, the reptiles had to forget to expand and contract their chests.

Notice that mammals, which use a diaphragm, still retain a bit of the reptilian system. So it's not surprising that the birds could gradually change, too.

Then they thought, Hey, it'd be a good idea to lose our diaphragms as well, so we can become birds.

What makes you think they had diaphragms?

Barbarian observes:
Once the collateral ventilation is established, the simplification of the lungs is possible by reducing the numerous alveoli to fewer air sacs, and by evolving one-way valves that increase the efficiency of the system.

Once more with feeling. Birds DO NOT HAVE ALVEOLI where air is exchanged.

Not now. We don't have gills, either. But we have structures that evolved from gills.

Barbarian observes:
This is just one of many ways it could have happened. It has the virtue of being consistent with the evidence from fossils.

In view of the above, don't you think it would be a good idea to give up at this point?

I can think of two reasons not to.

1. I'm presenting a great deal of evidence to support my position.

2. You aren't.

Here's Ruben on the subject:

That's nice, but an unsupported assertion isn't worth much in science. Evidence is required. And as you see, it's all on the side of bird lungs being modified reptilian ones.

That's putting it mildly, isn't it?

Yep.

 

[Barbarian]

Bird-like respiratory systems in dinosaurs -- A recent analysis showing the presence of a very bird-like pulmonary, or lung, system in predatory dinosaurs provides more evidence of an evolutionary link between dinosaurs and birds. First proposed in the late 19th century, theories about the animals' relatedness enjoyed brief support but soon fell out of favor. Evidence gathered over the past 30 years has breathed new life into the hypothesis. O'Connor and Claessens (2005) make clear the unique pulmonary system of birds, which has fixed lungs and air sacs that penetrate the skeleton, has an older history than previously realized. It also dispels the theory that predatory dinosaurs had lungs similar to living reptiles, like crocodiles.

The avian pulmonary system uses "flow-through ventilation," relying on a set of nine flexible air sacs that act like bellows to move air through the almost completely rigid lungs. Air sacs do not take part in the actual oxygen exchange, but do greatly enhance its efficiency and allow for the high metabolic rates found in birds. This system also keeps the volume of air in the lung nearly constant. O'Connor says the presence of an extensive pulmonary air sac system with flow-through ventilation of the lung suggests this group of dinosaurs could have maintained a stable and high metabolism, putting them much closer to a warm-blooded existence. "More and more characteristics that once defined birds--feathers, for example--are now known to have been present in dinosaurs, so, many avian features may really be dinosaurian," said O'Connor. A portion of the air sac actually integrates with the skeleton, forming air pockets in otherwise dense bone. The exact function of this skeletal modification is not completely understood, but one explanation theorizes the skeletal air pockets evolved to lighten the bone structure, allowing dinosaurs to walk upright and birds to fly.
Bird Respiratory System

 

[lordkalvan]

....Try explaining that fact. LK can say what he likes about personal incredulity, but until he can produce even the vestige of an EVOLUTIONARY explanation of these FACTS, then the case is dead in the water.

And yet all we have here is yet another example of personal incredulity: evolution cannot 'explain' X (yet it can) to your satisfaction (not achievable as you have already decided that evolution is impossible - yet it happens all the time), so - fanfare of trumpets - it follows that evolutionary theory is 'dead in the water'.

Birds are one of the largest groups of animals extant - and here is a simple fact which evolution cannot account for.

You mean just like evolution couldn't account for bats? Oh wait, it could.

When are you guys going to recognise it for what it is, i.e. useless at explaining any concrete facts? And give it up?

Maybe when you provide a better account of the evidence that better explains it under whatever paradigm you cling to. Meanwhile you could make a start by responding to all those points, arguments and questions arising from your assertions elsewhere that you have ignored, denied, misrepresented or trivialised.