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Author Topic:   Theropods and Birds showing a change in kinds
slevesque
Member (Idle past 1108 days)
Posts: 1456
Joined: 05-14-2009


Message 57 of 150 (545134)
02-01-2010 3:43 PM
Reply to: Message 55 by DC85
01-31-2010 5:03 PM


what would you consider a transition? and what needs to be observed to show the relation of two species? As far as Humans and chimps we not only have physical similarities but DNA and embryonic.

To be honest it confuses me when people say that isn't evidence. To add to that evidence we also have fossilized Hominid fossils.

What else is needed?

We briefly overlooked humanid evolution with huntard a bit earlier I believe. Since it wasn't in the subject I referred the book 'bones of contention'.

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. One of those options is convergent evolution. You need to find a physical criteria that can be observed that show convergent evolution took place and not common descent. Dr. Adequate said earlier that convergent evolution causes only superficial ressemblance but no in depth similarities. I have a hard time accepting this idea as valid, so maybe if it could be explained in detail and how a criteria for convergent evolution can be clearly stated out of this.


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Replies to this message:
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slevesque
Member (Idle past 1108 days)
Posts: 1456
Joined: 05-14-2009


Message 60 of 150 (545245)
02-02-2010 3:33 PM
Reply to: Message 58 by menes777
02-02-2010 11:56 AM


I think one of the faults with creationism is that it's mainly based on the arguments attempting to disprove rather than prove. That if you can disprove evolution than you prove creationism right. Evolution is the opposite and only attempts to prove what it can support not what it can disprove. Thus the objective here isn't to disprove everything except common descent but attempt to prove it with the evidence that we have.

This is a bit off-topic, but I'll give a brief answer anyways. Creationist don't solely have evidence against evolution, they also have evidence for creation.

Now, in the case of evidence against evolution, sure creationists uses them a lot. And they are not necessarily proof of a 6000 year old creation of the world obviously. Rather, arguments against the evolution of species simply becomes evidence for the statistity of species (in which of course the biblical creation fits well obviously)

Now, I think you misunderstood my statement there. I wasn't saying you have to disprove all other options in order to prove common descent. I was saying that if you want similarities alone to be sufficient proof for common descent, then you have to disprove all other options. Of course, anyone with some knowledge of philosophy of science will realise that this is an impossible feat to accomplish, and therefore similarities are unsufficient by themselves to prove common descent.

Didn't you mean this sentence to have common descent and convergent evolution to be switched? Also do you have any way to explain how convergent evolution applies to human and chimp evolution?

I meant this sentence as: In a given situation, is thee a way to show that common descent took plce and not convergent evolution?

Look at bird wings and look at bat wings. Both are wings and when viewed from afar they appear to be the same. Yet when examined closely the difference is obvious. Bird wings have feathers, bat wings do not. The bone structure of bat wings is different from bird wings. Therefore the similarities are only superficial.

Not the best example of convergent evolution, I prefer Taq's example with duck and platypus bills. Although everything I will say on that issue would probably apply to your example.


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slevesque
Member (Idle past 1108 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


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slevesque
Member (Idle past 1108 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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slevesque
Member (Idle past 1108 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 1108 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.


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slevesque
Member (Idle past 1108 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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slevesque
Member (Idle past 1108 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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slevesque
Member (Idle past 1108 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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slevesque
Member (Idle past 1108 days)
Posts: 1456
Joined: 05-14-2009


Message 87 of 150 (545628)
02-04-2010 3:16 PM
Reply to: Message 75 by DC85
02-04-2010 6:11 AM


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.

I think it is evidence of a creator, but not proof.

what would be compelling evidence? DNA isn't compelling to you. Transitional fossils aren't. ... What do we need to show you?

If the fossil record had really shown what was predicted of it, then I would have found this very compelling. However, the only model it does fit is the Ad Hoc explanation of ponctuated equilibrium.

Also, when the field of population genetics started back in the 50's, it opened up new ways to verify the ToE and in my opinion it only showed how it is impossible on a theoretical level. (see 'genetic entropy' by Sanford)

there is one and we have how many between humans and chimps?

I'm sorry to say it is beyond my knowledge since I don't even know what introns are. (or I do, but I don't know the french word for them)


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slevesque
Member (Idle past 1108 days)
Posts: 1456
Joined: 05-14-2009


Message 88 of 150 (545629)
02-04-2010 3:19 PM
Reply to: Message 76 by DC85
02-04-2010 6:26 AM


You gave an example of a bird that dates after the therapods. This is not surprising.

What I am saying is that there are birds found before the therapods, and so whatever whatever link between the two is found after that does not explain how those earlier birds came to be in the first place.


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slevesque
Member (Idle past 1108 days)
Posts: 1456
Joined: 05-14-2009


Message 90 of 150 (545634)
02-04-2010 3:40 PM
Reply to: Message 77 by caffeine
02-04-2010 7:19 AM


Re: Feathers as novel features
Hi caffeine,

Not all feathers are optimised for flight, though. There are a plethora of different types of feather - different species have different feathers, and the same species have different feathers on different parts of their body and at different stages in their life. Only a minority of these are the asymmetrical, pennaceous feathers perfectly suited for flight. Most birds begin life covered with fluffed-up downy feathers which aren't at all aerodynamic, but trap air quite well to insulate the little baby bird.

Ever seen baby ostriches covered with downy feathers ? Quite cute right, but now imagine it getting all wet. It will die of hypothermia within minutes if it's mother doesn't heat it up. For a species to be covered by such a structure for endothermy would be extremely maladaptive, to the point of being harmful.

And of course, no dinosaurs are found with downy feathers. They are either found with 'dinofuzz' or with true feathers which have a central rachis, etc. In fact, the dinofuzz is found not only on therapods, but also on icthyosaurs, pterosaurs and ornithischian dinosaurs. In none of these cases are they related to feathers, and there is nothing to suggest then that this should be the case with therapods.

Okay, I found the same quote in this article. He doesn't, however, back up the claim anywhere I can find, and despite all my rummaging on the internet, nowhere can I find mention anywhere of a Triassic bird fossil. This includes all the articles I looked at by and about the OSU researchers - were there really such support for this claim, I think they might have mentioned it.

I couldn't tell you. Contacting him directly to ask him might be the onl way of knowing what he meant.

Until we find any support for the claim I'll stop saying it

Even if we discount all the possible but dubious coelurosaurian and maniraptoran fossils that predate Archaeopteryx, we have a huge variety appearing alongside the birds in the late Jurassic and early Cretaceous. If we reject their common theropod ancestor, then we're forced to argue instead that a structure as complex as the feather evolved not just once, but twice, in basically the same form, at about the same time. This stretches credulity a bit.

Convergent evolution can do marvels. Exactly the same sonar structure up down to the genome level in dolphins and bats, for example.


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slevesque
Member (Idle past 1108 days)
Posts: 1456
Joined: 05-14-2009


Message 91 of 150 (545635)
02-04-2010 3:51 PM
Reply to: Message 78 by Dr Adequate
02-04-2010 7:44 AM


Re: Feathers as novel features
Hi Dr.A,

Creationists are going to distort whatever arguments come up, and they've put me in company with luminaries like Stephen Jay Gould, so it doesn't bother me a bit. Archaeopteryx is half reptile and half bird any way you cut the deck, and so it is a Rosetta stone for evolution, whether it is related to dinosaurs or not. These creationists are confusing an argument about minor details of evolution with the indisputable fact of evolution.

Yeah I have read some counter-quotes by Feduccia when searching a bit yesterday. I think it is fairly obvious thatwhat happened to him is the same that happened to Gould. He thought of a great alternative to the commonly accepted theory and started out in fanfare trying to promote it, with big claims etc. Of course, when some of those claims were picked up by creationists it hurt his reputation quite a bit, and to claim it back he stepped down a notch on his claims and even contradicted himself on some occasions, such as here. (which was an email answer to a question by a layman, I believe right ?)

In any case, he contradicts himself. It's normal with humans


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slevesque
Member (Idle past 1108 days)
Posts: 1456
Joined: 05-14-2009


Message 92 of 150 (545636)
02-04-2010 3:56 PM
Reply to: Message 79 by Dr Adequate
02-04-2010 8:15 AM


Which paleontologists can spot, which is the only reason you know that in the first place.

Did you read the interview with Feduccia I posted earlier ? He says that there are loads of fake fossils out there. Obviously, if they were easy to spot they wouldn't be 'out there'.

Or do you think only archaeoraptor was fake and all the others were legit ?


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slevesque
Member (Idle past 1108 days)
Posts: 1456
Joined: 05-14-2009


Message 94 of 150 (545639)
02-04-2010 4:03 PM
Reply to: Message 83 by Taq
02-04-2010 10:34 AM


So we have gone from "fingerprints are not compelling evidence" to "what fingerprints?".

Is that how a court of law works? Proof beyond a reasonable doubt once you have ignored the evidence?

The fact of the matter is that there are fossils with dinosaur characteristics not found in any living bird. These same fossils have avian features not found in other dinosaurs. How is this not half dino/half bird?

Don't worry, my intention is not to ignore evidence.

But in the case of fossils, you have either dinosaurs with feathers, but aside from that are completely dinosaurs. And birds with all the characteristics of birds (perching bird in the case of archaeopterix) with some reptile features like teeth if I remember correctly (and teeth isn't really a uniquely reptilian feature)

No really 50/50 in between type. No in between lung structure, no in between femur structure, no in between balance structure, etc.


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