The Evolution of Birds (Or: What missing link?)

[Walter L. Wagner]

I assume the advantage for the archosaur and its descendants would be more efficient breathing. The article in fact states: "The researchers who have discovered the system in alligators believe it may have given dinosaurs the competitive edge over the ancestors of mammals following the mass extinction at the end of the Permian period, 250 million years ago." So there, if you had read the article properly, is your answer.

My second paragraph would be refuted only if humans and octopi "appear closely related for other reasons" than the similarity (you've told us already there are not identical) between human and octopus eyes.

You do not seem to be very good at reading comprehension. However this is understandable if English is not your native language.

English is his native language. He's just being lazy on his reading. BillyT will likely acknowledge that.

But he had a good point about bird breathing system. And yes, as I said before and say again, it appears that that 'mystery' is solved, as dinosaurs likely had the similar system as birds (their desecendants) and crocodiles (their distant relatives).

As to Trippy's original article, there is a 'seamless transition' for every extant species today and their ancient ancestors. We just don't have as good a fossil record for many of them as we've developed for dinosaurs/protobirds/ancientbirds. This is likely because they were so prodigious they left more fossils; and they lived in areas where we've got a good fossilization (such as China)

 

[Trippy]

English is his native language. He's just being lazy on his reading.

That's one word for it.

BillyT will likely acknowledge that.

Not in my experience.

But he had a good point about bird breathing system.

No he didn't - the breathing system was one of the features mentioned explicitly in the article.

As to Trippy's original article, there is a 'seamless transition' for every extant species today and their ancient ancestors. We just don't have as good a fossil record for many of them as we've developed for dinosaurs/protobirds/ancientbirds.

This statement manages to completely miss the point of the article.

 

[Trippy]

One further thought: unless I'm misreading the diagram, all the examples shown are of those branches that are NOT in a line of direct ancestry to modern birds. Why is this? Could a diagram not be put together that shows some fossils that ARE on the direct line, at intermediate points?

Without this, it strikes me that this diagram could be a bit of a gift to a creationist - or would at least allow him some wiggle room.

The diagram is a phylogenetic diagram - basically it shows the relationships of species. It's showing that Dromaeosaurids, Troodontids, and modern birds had a common ancestor.
The common ancestor of those groups had a common ancestor with Oviraptorosaurs.
That common ancestor had a common ancestor with Therizinosaurs and Alvarezsaurs.
That common ancestor had a common ancestor with Ornithomimosaurs and Compsognathids.
That common ancestor had a common ancestor with Tyrannosaurs.

The progression, more or less is as you move from the top of the diagram to the bottom of the diagram.

 

[Trippy]

Trippy complained that I should not comment on the article that I did not read.

And you should not - making statements about what the article had better cover without reading the article is absurd. For all you know it covers that (and the breathing system is, in fact, one of the features that the article considers which makes your comments look even more ridiculous).

I did not. I only told two things:

This sentence is bad english. You did not 'tell' two things, you made to statements or you said two things.

(1) The main problem with dinosaur to bird evolution theory is the lack of any advantage to adding parts of the one way air flow design while continuing to keep all the parts of a viable two way air flow system the dinosaurs used. (For any change to be selected for, it must give some advantage, not be an extra developmental cost that would be selected against.)
Worse: No viable intermediate stage with advantage over the dinosaur's two way flow (in then out by same path for 50% duty cycle) has ever (to my knowledge) been suggested, much less one that gives any advantage.

Read the article - for all you know this is covered in it (or the original articles which are linked to from it).

(2) There are many cases where "mother nature" has INDEPENDANTLY evolved quite similar structures to do the same job. - Such as gathering information from distant part of the environment by sensing / observing the radiation coming from it. Typically there is an optimum solution to this and to most problems
and mother nature, given enough time comes close to finding it - Thus very similar structures, for example, a lens* with detectors in a curved 2D "focal plane" are what we find in many totally unrelated creatures.

In species that aren't closely related, sure, but we're not talking about distant relatives here.

 

[Walter L. Wagner]

The diagram is a phylogenetic diagram - basically it shows the relationships of species. It's showing that Dromaeosaurids, Troodontids, and modern birds had a common ancestor.

The progression, more or less is as you move from the top of the diagram to the bottom of the diagram.

It looks like all other phylogentic diagrams I've seen, but with not as much detail as most. Take a look at plant phylogenetic diagrams, with dozens of intermediaries between top to bottom.

The point of the article is that there is a good fossil record showing the change from full dinosaur to full bird. But that is what I said in my prior post.

 

[Trippy]

It looks like all other phylogentic diagrams I've seen, but with not as much detail as most. Take a look at plant phylogenetic diagrams, with dozens of intermediaries between top to bottom.

:Roll:
I thought you said you had read the article? Or did you read the entire article except the image caption which reads "Here’s a simplified version of their phylogenetic relationships"?

The point of the article is that there is a good fossil record showing the change from full dinosaur to full bird. But that is what I said in my prior post.

No.

The point of the article is that there has been an expectation within the paleontological community that there was some kind of missing link between dinosaurs and birds. Finding this has been an area of active research. What the article says is that upon a re-analysis of the fossil record as it currently stands it appears it may actually be complete and that there are no missing links in the transtion from dinosaurs to birds. It also suggests that this is because by the time birds evolved in the fossil record all (or most) of the features we associate with modern birds (one way breathing, air sacs, hollow bones, the wish bone, the keeling of the sternum, the lack of wrist bones, 853 features in 150 species in all) were already in place by the time birds evolved. It goes on to say that these features evolved over a period of tens of millions of years and once they were all in place birds underwent explosive diversification.

The point of the article is that rather than what we expected to see, which was Dinosaurs -> Intermediate missing link -> Birds, what actually happened was that one particular branch of the dinosaur family tree became increasingly birdy.

 

[Walter L. Wagner]

:Roll:
I thought you said you had read the article? Or did you read the entire article except the image caption which reads "Here’s a simplified version of their phylogenetic relationships"?


No.

The point of the article is that there has been an expectation within the paleontological community that there was some kind of missing link between dinosaurs and birds. Finding this has been an area of active research. What the article says is that upon a re-analysis of the fossil record as it currently stands it appears it may actually be complete and that there are no missing links in the transtion from dinosaurs to birds. It also suggests that this is because by the time birds evolved in the fossil record all (or most) of the features we associate with modern birds (one way breathing, air sacs, hollow bones, the wish bone, the keeling of the sternum, the lack of wrist bones, 853 features in 150 species in all) were already in place by the time birds evolved. It goes on to say that these features evolved over a period of tens of millions of years and once they were all in place birds underwent explosive diversification.

The point of the article is that rather than what we expected to see, which was Dinosaurs -> Intermediate missing link -> Birds, what actually happened was that one particular branch of the dinosaur family tree became increasingly birdy.

Except I was not expecting a "missing link" as I was already aware of the near-seamless transition in the fossil record, due to the large number of feathered dinos being found in China over the past few decades. Consequently, it did not come as a 'surprise' to me "that there are no missing links in the transtion from dinosaurs to birds", which as I stated "there is a good fossil record showing the change from full dinosaur to full bird", which is essentially what you stated.

That's not to say that we should quit looking for more feathered dinos, as we can always fill-in between the existing transitional forms, as well as detail the 'dead-end' forms that did not result in true birds, but died out.

 

[Trippy]

Yes I read your link - But want to know what advantage part of a one-way flow respiratory system gave?

Improved oxygen scavenging.

Your second paragraph is refuted by the essentially identical eyes of humans and octopi.

No it isn't.

Your point that one cannot assume similar structures evolved from each other is of course true in principle. The wing evolved at least three times independently, for example (insects, birds, mammals). However, when you have creatures with similar features that appear closely related for other reasons, it is still a reasonable working assumption unless there is evidence to the contrary.

Humans and Octopi are not closely related. Crocodiles and birds are both Archosaurs (the same clade) where Humans and Octopi aren't even the same phyllum (humans are Chordata, Octopi are Mollusca).

Do I really need to explain this in greater depth, or..?

 

[Trippy]

Except I was not expecting a "missing link"...

I'm not sure I was either :shrug: what's your point?

...as I was already aware of the near-seamless transition in the fossil record, due to the large number of feathered dinos being found in China over the past few decades.

There's a difference between suspecting something is probably true and being able to demonstrate it conclusively in a repeatable fashion in a peer reviewed journal.

That's not to say that we should quit looking for more feathered dinos, as we can always fill-in between the existing transitional forms, as well as detail the 'dead-end' forms that did not result in true birds, but died out.

There you go again with your feather fetish.

 

[Walter L. Wagner]

There you go again with your feather fetish.

Well, your article was all about feathered dinosaurs before they were true birds, was it not? Yes, they have other traits that are somewhat bird-like before they had feathers. But most of the transition shows feathered dinosaurs, which appeared somewhat surprising to paleontologists at the time of their discovery that they were full dinos (not bird-like at all; ie no wings or flight) but covered with feathers. And feather evolution is interesting, though not my 'fetish'

 

[Billy T]

Replying to exchemist's post 16: (for unknown reasons it doe not appear here with pink back ground.)

I don't care what "researchers BELIEVE MAY HAVE BEEN AN ADVNTAGE." I want some indication that there was one. Certainty there was extra biological cost to build in a system with little or no utility. Of course they MUST believe that if already thinking birds (and or alligators) came from dinosaurs and accept evolution's selection theory.

For example, most animals (all carnivores, I think) do have a system for making vitamin C, and early ancestors of the primate branch probably had it, but that cost was selected out of their DNA as they got all the vitamin C they needed from their diet. - this information comes to me from the only double winner of the noble prize (I think) - Linus Pauling. He ate 8 grams of vitamin C each day after studies of how much other animals produced per unit of body weight. - how he chose 8 grams.

There are uncountable number of examples of structure that were once useful being selected against and eliminated. Not one example of structure with no use (but a biological cost) being selected for.

Yes English* is my native language and I know the important difference between what some "experts believe" and evidence. Do you? Many believe in God - but that is not evidence.

* I am however a little dyslexic - Interestingly when I re-read my post as I have written them - I often fail to see the errors - read what should be there; however, when I do post, the change in form, sentence length or something makes it easier for me to notice my errors. I also often have let my thoughts get ahead of my typing and words have been left out (doing that to word "not" reverses my intent). So I typically edit my post several times, and not rarely someone replies before my post is in final form.

Replying to Walter Wagner's post 21 statement " We just don't have as good a fossil record for many of them as we've developed for dinosaurs/protobirds/ancientbirds.":

The way bird's rib bones are rigidly attached to the back bone should be clear and different from the way that dinosaur's (and man's) are more flexibly attached. - Birds do not expand their chest when breathing but man and dinosaurs do. That change, however, can have viable intermediate stages - the binary switches can not. (like evolving giraffe putting nerve on the other side of bone OR replacing two-way air system with a one-way flow system) This rigidly, only move membrane wall not bones and mussels, is another way that birds use less energy per gram of O2 intake.

 

[Walter L. Wagner]

The way bird's rib bones are rigidly attached to the back bone should be clear and different from the way that dinosaur's (and man's) are more flexibly attached. - Birds do not expand their chest when breathing but man and dinosaurs do. This is another way that birds use less energy per gram of O2 intake.

Clearly birds, once flight was first obtained, continued to optimize in that direction. Archaeopteryx is considered a 'true bird' though it has many primitive traits not present in modern birds. Did primitive birds have fixed ribs, or did that arise after birds were already flying? Certainly most primitive birds went extinct, and extant birds are derived from one lineage that proved superior to all others primitive birds.

 

[Billy T]

I don't know the answer to any of your questions, Walter. My point is that switching from two way flow to one way flow respiration is a "binary change" impossible for evolution to make in set of small evolutionary steps, each with an advantage. Just like putting the retina in front of the network of blood vessels and signal collection nerves, which join at the "blind spot" in man (retina behind all this) is an impossible binary change - no creature can do that.

It would have considerable advantages, which the octopus enjoys with a better eye design. Not only more light reaching the retina and no "blind spot" in each eye, but more importantly (I think) much of the neural processing in V1 is for filling in the blood vessel shadow gaps.

For example when you look at your dog - the optical data of its image sent to the brain is broken into at least 1000 separated "dog parts" by the blood vessel network shadows. - You must fill all these black shadow cuts with best guess of what color etc. was blocked out, in order to perceive a single dog image. - Every glance at any object requires V1 to put together a "jig saw puzzle" of pieces! The octopus brain is spared this task.

V1's task is much harder than just putting together all the separated tiny image parts of the dog as the 2D image of the dog has other tiny parts next to all the perimeter dog parts. For example the dog may be standing next to a tree. No one is telling V1 that the vertical trunk that in the 2D retinal image which seems to be coming out of the dog's back is not also part of the dog. - You don't know what is making the CONTINUOUS 2D stimulation of retinal cells until much later (out in the temporal lobes) that it is a dog and tree you are looking at.

To better appreciate the complexity of just parsing the continuous 2D retinal stimulation into discrete objects for later parts of the brain to identify, imagine I gave you a black and white photo taken at a foot ball game showing the field and fans in the stadium on the other side, but I cut that 8 by 10 inch photo in to a set of 100,000 tiny pieces of random shape. Your brain solves this problem several times each second as the dog image parts fall on different parts of the retina with each fixation and all the tiny dog image pieces then have different shapes! God was very kind to the octopus, if evolution is wrong - as his retinal blood supply is behind the retina - Thus dog is one image area, not 5000 tiny odd shaped pieces that differ in shape with each new fixation.

 

[Trippy]

I don't know the answer to any of your questions, Walter. My point is that switching from two way flow to one way flow respiration is a "binary change" impossible for evolution to make in set of small evolutionary steps, each with an advantage. Just like putting the retina in front of the network of blood vessels and signal collection nerves, which join at the "blind spot" in man (retina behind all this) is an impossible binary change - no creature can do that.

It would have considerable advantages, which the octopus enjoys with a better eye design. Not only more light reaching the retina and no "blind spot" in each eye, but more importantly (I think) much of the neural processing in V1 is for filling in the blood vessel shadow gaps.

For example when you look at your dog - the optical data of its image sent to the brain is broken into at least 100 separated "dog parts" by the blood vessel network shadows. - You must fill all these black shadow cuts with best guess of what color etc. was blocked out, in order to perceive a single dog image. - Every glance at any object requires V1 to put together a "jig saw puzzle" of pieces! The octopus brain is spared this task.

V1's task is much harder than just putting together all the separated tiny image parts of the dog as the 2D image of the dog has other tiny parts next to all the perimeter dog parts. For example the dog may be standing next to a tree. No one is telling V1 that the vertical trunk that in the 2D retinal image seems to be coming out of the dog's back is not also part of the dog. - You don't know what is making the CONTINUOUS 2D stimulation of retinal cells until much later (out in the temporal lobes) that it is a dog and tree you are looking at.

Billy T you're talking about two seperate changes - the morpheological changes required for the avian flow throigh system of breathing will still work with tidal breathing. From their it's a matter of changing the timing of muscle contractions from tidal breathing to unidirectional flow through. Bidirectional flow through still works in lungs optimized for unidirectional flow through.

 

[Billy T]

Billy T you're talking about two seperate changes - the morpheological changes required for the avian flow throigh system of breathing will still work with tidal breathing. From their it's a matter of changing the timing of muscle contractions from tidal breathing to unidirectional flow through. Bidirectional flow through still works in lungs optimized for unidirectional flow through.

That {"Bidirectional flow through still works in lungs optimized for unidirectional flow through."} may be true but if you have two extra sacks within the chest (one for holding briefly the full intake volume, while the other equally large one contracts to exhale the full stale air breath volume) then your actual lung volume will be greatly reduced - less than half the size it could be without those two additional sacks - that is disadvantage that would be selected AGAINST. If any baby of two-way flow parents were so deformed as to have added two useless sacks it probably would not even be a viable birth defect! Trying to slowly evolve the extra sacks, control system etc, via many generation is equally impossible - no advantage at any tiny step change.

Hey - You text posted in pink. - Only thing I did differently was to hit the return arrow as I had forgotten to copy the part of your text I made bold above. I.e. I again right clicked on the "reply" next to your post number.

 

[Trippy]

I'm not sure i accept your argument regarding air-sacs.

The flipside is that Crocodiles and alligators have been shown to have one way air flow even though they lack air sacs and use diaphramatic breathing.

 

[Walter L. Wagner]

That {"Bidirectional flow through still works in lungs optimized for unidirectional flow through."} may be true but if you have two extra sacks within the chest (one for holding briefly the full intake volume, while the other equally large one contracts to exhale the full stale air breath volume) then your actual lung volume will be greatly reduced - less than half the size it could be without those two additional sacks - that is disadvantage that would be selected AGAINST. If any baby of two-way flow parents were so deformed as to have added two useless sacks it probably would not even be a viable birth defect! Trying to slowly evolve the extra sacks, control system etc, via many generation is equally impossible - no advantage at any tiny step change.

BillyT. I re-post Exchemist's link: http://www.thedailybeast.com/articl...-can-t-say-his-spies-underestimated-isis.html#

It would not have to be a full chamber; a slow change would be very possible, with increasing 2-nd storage space capacity for one-way flow being the optimum.
Indeed, I suspect that the feathered dinosaurs, which were likely hibh-metabolism and needing to keep warm like mammals, had this fully developed long before the birds arose from them. Fixing the ribs would have been advantageous once flight began, as the flexing was no longer required, and a rigid structure would be advantageous for wing movement.

 

[Walter L. Wagner]

BillyT. I re-post Exchemist's link: http://www.thedailybeast.com/articl...-can-t-say-his-spies-underestimated-isis.html#

It would not have to be a full chamber; a slow change would be very possible, with increasing 2-nd storage space capacity for one-way flow being the optimum.
Indeed, I suspect that the feathered dinosaurs, which were likely hibh-metabolism and needing to keep warm like mammals, had this fully developed long before the birds arose from them. Fixing the ribs would have been advantageous once flight began, as the flexing was no longer required, and a rigid structure would be advantageous for wing movement.

oops; wrong link: here is the right one: http://www.newscientist.com/article...y-explain-dinosaurs-triumph.html#.VCg-Fkvlduo

darn that loss-of-edit function

 

[Trippy]

BillyT. I re-post Exchemist's link: http://www.thedailybeast.com/articl...-can-t-say-his-spies-underestimated-isis.html#

It would not have to be a full chamber; a slow change would be very possible, with increasing 2-nd storage space capacity for one-way flow being the optimum.
Indeed, I suspect that the feathered dinosaurs, which were likely hibh-metabolism and needing to keep warm like mammals, had this fully developed long before the birds arose from them. Fixing the ribs would have been advantageous once flight began, as the flexing was no longer required, and a rigid structure would be advantageous for wing movement.

I don't know about fixed ribs, but unidirectional airflow would certainly ne advantageous for small and/or fast moving dinosaurs.

 

[Billy T]

The flipside is that Crocodiles and alligators have been shown to have one way air flow even though they lack air sacs and use diaphramatic breathing.

yes: "Alligators don't have air sacs like birds, but the researchers think an unusual airway that sits on either side of the alligator trachea may do the same job." Adding sort of side slits like a shark has to allow more rapid exhaling is a beneficial first step so can be selected for. later as a second step letting slight suction close them is also beneficial - you are sort of in the better one way path then.

In your other post I agree that small (or even large) dinosaurs would benefit form having the more efficient one-way air flow respiration, but so would humans benefit if the retina were in front of instead of behind the neural network collecting signals (and the blind spot where those nerves converge to become the optic nerve) and also in front of the blood supply instead of behind it as their shadows cut the 2D image of each object into many tiny pieces but these are IMPOSSIBLE binary step changes - not small sort of analogue incremental changes that can accumulate over thousand of generations. I.e. add a pair of small air storage sacks (which the alligator could not, and did not, do ) to a two-way air flow system has "negative utility" and would be selected AGAINST. Like wise adding two big ones, all new "plumbing" and new and working control system in one generation would be a very very improbable "hopeful monster." - I.e. would be a fatal birth defect if not a complete functional system.