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Author Topic:   Theropods and Birds showing a change in kinds
slevesque
Member (Idle past 1054 days)
Posts: 1456
Joined: 05-14-2009


Message 61 of 150 (545247)
02-02-2010 3:46 PM
Reply to: Message 59 by Taq
02-02-2010 12:27 PM


If we applied this same criteria to all ideas then nothing could be known for sure. I can't even prove that I woke up this morning since it is possible that the universe was poofed into being just 5 minutes ago, complete with a false history and false memories.

Proof through disproof is a very poor way of seeking knowledge, IMHO. Proof itself, in the absolute sense, is unattainable. What we can do is see if a model makes testable predictions, and then test those predictions. That is what science does. It tests models.

Exactly the point I wanted to make. It would be impossible to disprove every other option to explain the similarities. I was just saying that if you wanted to use similarities as sufficient proof for common descent, this would have to be done. Since it cannot be done, then similarities can never be sufficient proof of common descent. This is just another path I took to explain the same thing I had previously in the thread, but new people had jumped into the discussion and asked why I didn't find similarities to be compelling proof of common descent.

A good example is the bill of the platypus and the bill of the duck. These two features do resemble each other superficially, but what happens when we look at the details? It turns out that the two bills are quite different:

Duck:

1. lower jaw is made up of three bones as in other birds.
2. bill is covered by horn.
3. Nares are near the base of the bill.
4. upper jaw is made of solid bone.

Platypus:

1. lower jaw is made up of a single dentary bone as in other mammals.
2. bill is covered in skin.
3. Nares are near the end of the bill.
4. Upper jaw has a split palate.

Here is a picture of the two skeletal structures:

Duck:

Platypus:

If all you saw was the skeletal structure you would never suggest that they were anything alike, or at least I wouldn't.

Excellent example. So you would agree that convergent evolution will only provide superficial similarities, never in depth ones ?

As to common descent v. convergence the test is in the DNA. Convergence can not produce a nested hierarchy at the DNA level for a whole genome. It is possible to do so for a couple mutations here and there, but practically impossible at the genome level. There is simply no mechanism by which a mutation in mice will cause the same mutation to occur in humans, as one example.

I agree this would be expected. However, recently I came across a counter-example where convergent evolution had caused the similarities to be right down to the molecular level. It is about the sonars of bats and dolphins which acquired the same DNA for this characteristics through convergent evolution:

http://www.sciencedaily.com/...ases/2010/01/100125123219.htm


This message is a reply to:
 Message 59 by Taq, posted 02-02-2010 12:27 PM Taq has responded

Replies to this message:
 Message 62 by Taq, posted 02-02-2010 4:20 PM slevesque has responded

  
Taq
Member
Posts: 5182
Joined: 03-06-2009
Member Rating: 2.5


Message 62 of 150 (545249)
02-02-2010 4:20 PM
Reply to: Message 61 by slevesque
02-02-2010 3:46 PM


Exactly the point I wanted to make. It would be impossible to disprove every other option to explain the similarities. I was just saying that if you wanted to use similarities as sufficient proof for common descent, this would have to be done.

You didn't get my point. "Sufficient proof" is an oxymoron in the same way that "partial vacuum" is an oxymoron. Either you have absolute proof or you don't. There is no halfway point.

However, we can have evidence. In the case of common ancestry, transitional fossils are evidence, quite compelling evidence IMO. More importantly, it is the pattern of homology in transitionals which evidences common ancestry.

That pattern is a nested hierarchy. This is what makes the theory of evolution a testable model. The theory predicts that there were species with a mixture of non-avian dinosaur features and avian features. The theory also predicts that there were NOT species with a mixture of mammalian and avian features. This allows us to see if fossils fit the predictions or not. They do fit the predictions. Therefore, the theory of evolution is a well evidenced theory.

So you would agree that convergent evolution will only provide superficial similarities, never in depth ones ?

Not always, no. It can be difficult to discern some adaptations as either due to common ancestry or convergent evolution.

I agree this would be expected. However, recently I came across a counter-example where convergent evolution had caused the similarities to be right down to the molecular level. It is about the sonars of bats and dolphins which acquired the same DNA for this characteristics through convergent evolution:

You will notice that I did say this:

"It is possible to do so for a couple mutations here and there, but practically impossible at the genome level."

It is the whole genome comparison between bats and cetaceans which indicates convergent evolution. A good test would be to compare the introns between the prestin genes in both bats and cetaceans.

Edited by Taq, : No reason given.


This message is a reply to:
 Message 61 by slevesque, posted 02-02-2010 3:46 PM slevesque has responded

Replies to this message:
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caffeine
Member (Idle past 95 days)
Posts: 872
From: Prague, Czech Republic
Joined: 10-22-2008


Message 63 of 150 (545312)
02-03-2010 5:22 AM
Reply to: Message 51 by slevesque
01-29-2010 4:07 PM


Re: Feathers as novel features
quote:
Ok, but don't these 'ginger structures' come from a previous structure in therapods ? If this wasn't scales, what was it ?

Good question, and one I'm not sure I'm qualified to answer. Thing is, they might not have needed much of a previous structure to come from. Before any of these structures were discovered in theropods, Richard Prum, one of the world's experts on feathers, had proposed a model of feather evolution based on how they developed in the embryology of modern birds. What he predicted as 'Stage 1' in this evolution was an undifferentiated, hollow cylinder of beta-keratin. That is pretty much what we seem to have discovered in theropods. The question then becomes, how much of an ancestral structure do you need in order to evolve hollow, undifferentiated filaments of a protein already present in your skin? It could be that only a small genetic change was needed to produce these things, and once there they worked as rudimentary insulation until they could be refined for display purposes and, later, flight (I'm guessing here, though).

After much rummaging, I finally managed to find an open-access copy of Prum's 1999 article - Development and Evolutionary Origin of Feathers (JOURNAL OF EXPERIMENTAL ZOOLOGY (MOL DEV EVOL) 285:291306 (1999)). I haven't had time to read it yet, but I'll have a look and see if I can get back to you with more details.

-----------------------------------------------------------------------

You mentioned in another post that birds have been around longer then theropods, but this isn't right. The earliest theoropd we've found may be Eoraptor, which is from rocks between the border of the Middle and Late Triassic, right back at the times of the earliest dinosaurs. Not everyone agrees this is a theropod, with some arguing it's a more primitive dinosaur. By the end of the Triassic, though, we have dinosaurs like the Coelophysoids, which everybody agrees are theropods. The oldest Coelophysoid we've found so far comes from the late Triassic of New Mexico, estimated at about 215 million years ago.

The oldest birds we've discovered are still, as far as I can tell, Archaeopteryx and others from about the same time period. These all come from the late Jurassic, more than 50 million years after the early coelophysoids. Nothing's been discovered to suggest that birds predate theropod dinosaurs yet.


This message is a reply to:
 Message 51 by slevesque, posted 01-29-2010 4:07 PM slevesque has responded

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RAZD
Member
Posts: 15828
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 1.9


Message 64 of 150 (545334)
02-03-2010 7:41 AM
Reply to: Message 63 by caffeine
02-03-2010 5:22 AM


Re: Feathers as novel features
Hi caffeine,

... Richard Prum, one of the world's experts on feathers, had proposed a model of feather evolution based on how they developed in the embryology of modern birds. What he predicted as 'Stage 1' in this evolution was an undifferentiated, hollow cylinder of beta-keratin. That is pretty much what we seem to have discovered in theropods. The question then becomes, how much of an ancestral structure do you need in order to evolve hollow, undifferentiated filaments of a protein already present in your skin?

What's the difference between a feather follicle and a hair follicle?

Enjoy.


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This message is a reply to:
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Peepul
Member (Idle past 1432 days)
Posts: 206
Joined: 03-13-2009


Message 65 of 150 (545343)
02-03-2010 8:35 AM
Reply to: Message 57 by slevesque
02-01-2010 3:43 PM


quote:
You ask what ese is needed. For similarities to be conclusive proof of common descent, you need to be able to prove that all other options aren't possible.

Slevesque, we do not need to go down that road. What we do is look at multiple strands of independent evidence pointing to common descent, not just physical similarity. When multiple stands suggest the same conclusion, we can accept we have probably found the right answer.

AbE - Slevesque, having read one of your latest posts, I think you'll agree with me!

To me whether any one strand is sufficient on its own is a non-question.

Edited by Peepul, : No reason given.


This message is a reply to:
 Message 57 by slevesque, posted 02-01-2010 3:43 PM slevesque has responded

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slevesque
Member (Idle past 1054 days)
Posts: 1456
Joined: 05-14-2009


Message 66 of 150 (545392)
02-03-2010 3:03 PM
Reply to: Message 65 by Peepul
02-03-2010 8:35 AM


I agree completely. This is what I'm trying to say all along.

Of course, those who have been saying that there isn't only one line of evidence will have understood this as well. It's more for those who ask: ''why doesn't this similarity between this one and that one convince you ?''


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 Message 65 by Peepul, posted 02-03-2010 8:35 AM Peepul has not yet responded

  
slevesque
Member (Idle past 1054 days)
Posts: 1456
Joined: 05-14-2009


Message 67 of 150 (545394)
02-03-2010 3:10 PM
Reply to: Message 63 by caffeine
02-03-2010 5:22 AM


Re: Feathers as novel features
Good question, and one I'm not sure I'm qualified to answer. Thing is, they might not have needed much of a previous structure to come from. Before any of these structures were discovered in theropods, Richard Prum, one of the world's experts on feathers, had proposed a model of feather evolution based on how they developed in the embryology of modern birds. What he predicted as 'Stage 1' in this evolution was an undifferentiated, hollow cylinder of beta-keratin. That is pretty much what we seem to have discovered in theropods. The question then becomes, how much of an ancestral structure do you need in order to evolve hollow, undifferentiated filaments of a protein already present in your skin? It could be that only a small genetic change was needed to produce these things, and once there they worked as rudimentary insulation until they could be refined for display purposes and, later, flight (I'm guessing here, though).

After much rummaging, I finally managed to find an open-access copy of Prum's 1999 article - Development and Evolutionary Origin of Feathers (JOURNAL OF EXPERIMENTAL ZOOLOGY (MOL DEV EVOL) 285:291306 (1999)). I haven't had time to read it yet, but I'll have a look and see if I can get back to you with more details.

A lot of the criticism I read yesterday by Alan Feduccia were very interesting and I think a little research on what he has to say would be helpful. I'll try to find some bits to put here.

I think the main logic in his discours is this: if feathers are so perfectly optimized for flight, why would anyone suggest they in fact evolved for endothermy (for which they are a sub-optimal structure, both in efficiency and in production cost)

You mentioned in another post that birds have been around longer then theropods, but this isn't right. The earliest theoropd we've found may be Eoraptor, which is from rocks between the border of the Middle and Late Triassic, right back at the times of the earliest dinosaurs. Not everyone agrees this is a theropod, with some arguing it's a more primitive dinosaur. By the end of the Triassic, though, we have dinosaurs like the Coelophysoids, which everybody agrees are theropods. The oldest Coelophysoid we've found so far comes from the late Triassic of New Mexico, estimated at about 215 million years ago.

The oldest birds we've discovered are still, as far as I can tell, Archaeopteryx and others from about the same time period. These all come from the late Jurassic, more than 50 million years after the early coelophysoids. Nothing's been discovered to suggest that birds predate theropod dinosaurs yet.

I had this information from prof. John Ruben of OSU (who was involved in the previous research who held that birds do not descend from dinosaurs):

"For one thing, birds are found earlier in the fossil record than the dinosaurs they are supposed to have descended from," Ruben said. "That's a pretty serious problem, and there are other inconsistencies with the bird-from-dinosaur theories.

Maybe are there some very old birds found in the fossil record, but since they don't fit that well with the dinosaur-to-bird theory you don't hear as much about them as Archaeopteryx.


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Replies to this message:
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slevesque
Member (Idle past 1054 days)
Posts: 1456
Joined: 05-14-2009


Message 68 of 150 (545395)
02-03-2010 3:26 PM
Reply to: Message 62 by Taq
02-02-2010 4:20 PM


You didn't get my point. "Sufficient proof" is an oxymoron in the same way that "partial vacuum" is an oxymoron. Either you have absolute proof or you don't. There is no halfway point.

I disagree. You have 'proof beyond reasonable doubt'. In other words, some things can be proven to a point where any doubt you can have will be unreasonable, illogical. This isn't absolute proof, but it isn't no proof at all either.

If you doubt that this is the case, just look at our law system and how courts prove someone guilty or innocent. Do you think they ever obtain absolute proof ? Of course not, but it doesn't mean they send people in jail with no proof at all. They prove people guilty 'beyond reasonable doubt'. Of course sometimes they do mistakes, but this is simply a side-effect of being unable to provide absolute proof.

However, we can have evidence. In the case of common ancestry, transitional fossils are evidence, quite compelling evidence IMO. More importantly, it is the pattern of homology in transitionals which evidences common ancestry.

I'm afraid I don't find transitional fossils to be compelling evidence at all.

AbE. I meant here to say that the concept of transitional fossils is good, but that the current evidence in it is what I do not find compelling.

You will notice that I did say this:

"It is possible to do so for a couple mutations here and there, but practically impossible at the genome level."

Isn't the coding of a complete structure as complex as a sonar more then just 'a couple of mutations here and there' and is in fact at the genome level.

It is the whole genome comparison between bats and cetaceans which indicates convergent evolution. A good test would be to compare the introns between the prestin genes in both bats and cetaceans.

Maybe I guess. But my point was that if convergent evolution can produce structures in two independant species that are the same even at the DNA level, then there is no way to know if it couldn't have done the same with these introns you are talking about. (I have basic knowledge in biology, probably equal to first year university stuff)

Edited by slevesque, : No reason given.


This message is a reply to:
 Message 62 by Taq, posted 02-02-2010 4:20 PM Taq has responded

Replies to this message:
 Message 69 by Taq, posted 02-03-2010 4:12 PM slevesque has responded
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Taq
Member
Posts: 5182
Joined: 03-06-2009
Member Rating: 2.5


Message 69 of 150 (545406)
02-03-2010 4:12 PM
Reply to: Message 68 by slevesque
02-03-2010 3:26 PM


I disagree. You have 'proof beyond reasonable doubt'. In other words, some things can be proven to a point where any doubt you can have will be unreasonable, illogical. This isn't absolute proof, but it isn't no proof at all either.

Even you seem to reject this idea, as evidenced by this statement:

"I'm afraid I don't find transitional fossils to be compelling evidence at all."

That is unreasonable and illogical. Using your analogy to a court case, it is equivalent to saying "I don't find fingerprint evidence all that compelling". Even worse, this unreasonable doubt is used to cast further doubt on the DNA evidence. "Since I reject the fingerprint evidence all you are left with is the DNA evidence which is just one small piece of evidence, so I reject that as well."

Isn't the coding of a complete structure as complex as a sonar more then just 'a couple of mutations here and there' and is in fact at the genome level.

Yes, it is at the genome level. However, the example you gave was for a single gene, not the whole genome.

"A hearing gene known as prestin in both bats and dolphins (a toothed whale) has picked up many of the same mutations over time, the studies show."
http://www.sciencedaily.com/...ases/2010/01/100125123219.htm

Edited by Taq, : No reason given.


This message is a reply to:
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Replies to this message:
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slevesque
Member (Idle past 1054 days)
Posts: 1456
Joined: 05-14-2009


Message 70 of 150 (545411)
02-03-2010 4:30 PM
Reply to: Message 69 by Taq
02-03-2010 4:12 PM


Even you seem to reject this idea, as evidenced by this statement:

"I'm afraid I don't find transitional fossils to be compelling evidence at all."

That is unreasonable and illogical. Using your analogy to a court case, it is equivalent to saying "I don't find fingerprint evidence all that compelling". Even worse, this unreasonable doubt is used to cast further doubt on the DNA evidence. "Since I reject the fingerprint evidence all you are left with is the DNA evidence which is just one small piece of evidence, so I reject that as well."

Yeah sorry, I misexpressed myself in that sentence. I wanted to say that I don't find the current actual transitional fossils to be compelling, not the general concept of transitional fossils.


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 Message 69 by Taq, posted 02-03-2010 4:12 PM Taq has responded

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Taq
Member
Posts: 5182
Joined: 03-06-2009
Member Rating: 2.5


Message 71 of 150 (545419)
02-03-2010 4:43 PM
Reply to: Message 70 by slevesque
02-03-2010 4:30 PM


Yeah sorry, I misexpressed myself in that sentence. I wanted to say that I don't find the current actual transitional fossils to be compelling, not the general concept of transitional fossils.

What reasonable and logical justification can you give for this position? Staying with the OP, can you justify your reasoning for rejecting multiple half-dinosaur/half-bird fossils as evidence of an evolutionary transition between dinos and birds?


This message is a reply to:
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slevesque
Member (Idle past 1054 days)
Posts: 1456
Joined: 05-14-2009


Message 72 of 150 (545435)
02-03-2010 5:16 PM
Reply to: Message 71 by Taq
02-03-2010 4:43 PM


What reasonable and logical justification can you give for this position? Staying with the OP, can you justify your reasoning for rejecting multiple half-dinosaur/half-bird fossils as evidence of an evolutionary transition between dinos and birds?

There exists no half dinosaur/half bird fossils. And I have already mentioned that birds appear before their supposed ancestors in the fossil record, and probably before the vast majority of the supposed transitional fossils.

Add to that the fact that there are a lot of fake dinosaur-bird fossils out there coming from china as per Alan Feduccia, and it seems that me skeptical is a justified and rational position.


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 Message 71 by Taq, posted 02-03-2010 4:43 PM Taq has responded

Replies to this message:
 Message 73 by ZenMonkey, posted 02-03-2010 10:12 PM slevesque has responded
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 Message 79 by Dr Adequate, posted 02-04-2010 8:15 AM slevesque has responded
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ZenMonkey
Member (Idle past 925 days)
Posts: 428
From: Portland, OR USA
Joined: 09-25-2009


Message 73 of 150 (545499)
02-03-2010 10:12 PM
Reply to: Message 72 by slevesque
02-03-2010 5:16 PM


Wait a sec.
slevesque, why are you bothering with fossils anyway, since you - if you are indeed a YEC - believe that the world's age is measured only in thousands of years, not millions or billions?
This message is a reply to:
 Message 72 by slevesque, posted 02-03-2010 5:16 PM slevesque has responded

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 Message 74 by slevesque, posted 02-03-2010 11:50 PM ZenMonkey has responded

  
slevesque
Member (Idle past 1054 days)
Posts: 1456
Joined: 05-14-2009


Message 74 of 150 (545509)
02-03-2010 11:50 PM
Reply to: Message 73 by ZenMonkey
02-03-2010 10:12 PM


Re: Wait a sec.
Hi ZM,

Yes a very good question at that. When I talk about fossils and how they relate to the ToE, I will assume the ages assigned to them in order to find a discussion ground to focus on the topic.

Because if I had to come in and say ''well I think the dates are wrong anyways'', we can all see that the subject would quickly change to radiometric dating etc. etc.


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DC85
Member (Idle past 177 days)
Posts: 854
From: Richmond, Virginia USA
Joined: 05-06-2003


Message 75 of 150 (545533)
02-04-2010 6:11 AM
Reply to: Message 68 by slevesque
02-03-2010 3:26 PM


quote:
I'm afraid I don't find transitional fossils to be compelling evidence at all.
do you find the complexity of life as proof of a creator? I know this is off topic however I find important to ask as such and assumption is a far larger stretch.

quote:
AbE. I meant here to say that the concept of transitional fossils is good, but that the current evidence in it is what I do not find compelling.
what would be compelling evidence? DNA isn't compelling to you. Transitional fossils aren't. ... What do we need to show you?

quote:
Maybe I guess. But my point was that if convergent evolution can produce structures in two independant species that are the same even at the DNA level, then there is no way to know if it couldn't have done the same with these introns
there is one and we have how many between humans and chimps?

Edited by DC85, : No reason given.


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