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Author Topic:   Transitional fossils and quote mining
caffeine
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Posts: 1655
From: Prague, Czech Republic
Joined: 10-22-2008
Member Rating: 5.7


Message 24 of 210 (524228)
09-15-2009 4:44 AM
Reply to: Message 15 by greyseal
09-14-2009 3:20 PM


Eggs
Platypus and echidna eggs are soft and leathery like reptile eggs, though, whereas bird eggs have a harder outer shell.
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caffeine
Member
Posts: 1655
From: Prague, Czech Republic
Joined: 10-22-2008
Member Rating: 5.7


Message 37 of 210 (524419)
09-16-2009 12:03 PM
Reply to: Message 33 by Arphy
09-16-2009 7:32 AM


What Feduccia Meant
Hello Arphy. I just wanted to quickly address these different comments from Feduccia, and what he was trying to say, as I think you've misunderstood them if you're still seeing a contradiction.

First we have this:

quote:
Archaeopteryx is half reptile and half bird any way you cut the deck

So, he is in agreement with every biologist in the world that Archaeoteryx is a transitional form between reptiles and birds. This is the common ground they were working from at the conference. But this isn't actually a very big common ground when it comes to discussing how Archaeoteryx behaved, or the specifics of its ancestry. Could it already fly, or were its wings used for some other purpose, for example? Did it behave like its coelurosaur ancestors and live as a ground-based predator, or had it developed another lifestyle? Is it actually evolved from a different reptile group than dinosaurs, meaning we shouldn't look to them for clues to its way of life? This is the context in which the next quote is meant:

quote:
Paleontologists have tried to turn Archaeopteryx into an earth-bound, feathered dinosaur. But it's not. It is a bird, a perching bird.

He's saying that Archaeopteryx did not live like a coelurosaur. It wasn't 'earth-bound' as some palaeontologists claim, meaning that it was capable of flight. He describes it as a perching bird, meaning it probably spent little time on the ground, perhaps catching its prey in the air and resting on tree branches.

Whichever side of this debate you fall on, however, it doesn't contradict the initial statement that Archaeopteryx is transitional between reptiles and birds. He just sees their ancestry in a different group of reptiles, and disagrees with the rest on how it lived.


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 Message 38 by Hyroglyphx, posted 09-16-2009 12:11 PM caffeine has not yet responded

  
caffeine
Member
Posts: 1655
From: Prague, Czech Republic
Joined: 10-22-2008
Member Rating: 5.7


Message 40 of 210 (524491)
09-17-2009 6:56 AM
Reply to: Message 39 by Arphy
09-17-2009 6:11 AM


Re: Lies, Damn Lies and Creationist Quote Mines
Feduccia:
Did you (and Caffeine) even read this:
quote:
Of course he may be of the opinion that birds did not evolve from dinosaurs but some other reptile, which i guess might accomadate the two quotes but that doesn't help you guys because you seem to suggest that you believe that birds did evolve from dinos.

Oops. I did read this, but it somehow failed to register in my brain. Maybe this is the same psychological mechanism that allows for quote mining in the first place.

Given that the Archaeopteryx quote was being presented in a context where it purported to provide expert support for the view that it is not transitional between reptiles and birds.

Now, he wouldn't be much use if we were using his arguments to support the view that Archaeopteryx evolved from dinosaurs, but we weren't. We were simply pointing out you were incorrect to use it as support for this position:

"If, of course, itís a true bird, it is not the half-way, half-reptile, half-bird like we've often heard."

Those who argued it was a true bird at the conference still considered it transitional between birds and reptiles.


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caffeine
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Posts: 1655
From: Prague, Czech Republic
Joined: 10-22-2008
Member Rating: 5.7


Message 53 of 210 (524545)
09-17-2009 12:18 PM
Reply to: Message 46 by greyseal
09-17-2009 9:17 AM


Re: All dinosaurs
There were many different reptile groups that coexisted with dinosaurs. There were the ancestors of modern day tortoises and turtles, and all their relatives, as well as the ancestors of lizards and snakes and all their relatives, for example. Feduccia agrees with everyone else that birds are archosaurs (the group of reptiles that includes crocodiles, crurotarsans, pterosaurs, dinosaurs, plesiosaurs (I think) and many more), he just thinks that the ancestors of birds split off from the dinosaurs earlier in archosaur evolution.
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caffeine
Member
Posts: 1655
From: Prague, Czech Republic
Joined: 10-22-2008
Member Rating: 5.7


Message 82 of 210 (525065)
09-21-2009 12:52 PM
Reply to: Message 77 by Arphy
09-21-2009 7:45 AM


Haldane's dilemma
quote:
Take a population of 100,000. If only a male and female pair have the new trait, natural selection must eliminate the other 99,998 and all their heirs. If there is perfect selection (s = 1), this can happen in one generation. But this means that for every new trait, 49,999 individuals must be eliminated without offspring. Then the population must be regenerated with these survivors.

Just a quick point. This is clearly not true, for obvious reasons. The 99,998 individuals being eliminated isn't particularly difficult, since they'll all die at some point and no-one would expect this mutation to spread throughout the whole population in a single generation. More importantly, their heirs do not all need to be eliminated. Some of them may mate with the mutated pair or their descendants; or their descendants may do so. This way, many of the descendants of individuals without the mutation may wind up possessing the mutation. The magic of sex.


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caffeine
Member
Posts: 1655
From: Prague, Czech Republic
Joined: 10-22-2008
Member Rating: 5.7


Message 135 of 210 (525701)
09-24-2009 10:22 AM
Reply to: Message 130 by Arphy
09-24-2009 8:20 AM


Beneficial and deleterious mutations
quote:
Mutations are not uniquely biological events that provide an engine of natural variation for natural selection to work upon and produce all the variety of life. Mutation is the purely physical result of the all-pervading mechanical damage that accompanies all molecular machinery. As a consequence, all multicellular life on earth is undergoing inexorable genome decay because the deleterious mutation rates are so high, the effects of the individual mutations are so small, there are no compensatory beneficial mutations and natural selection is ineffective in removing the damage.

This isn't so much a conclusion, as an assertion. Conclusions tend to be supported by the arguments offered in the body of a work, whereas this isn't.

At no point is it explained how we can declare all mutations to be damaging. I noticed that one of the examples of an observed mutation picked in the article is melanism, which it concedes may be tangentially beneficial in some environments. But, for what reason is melanism declared deleterious, damaging or degenerative in the first place? Other than a bizarre argument based on trans-species racism, I can't see where they would be coming from. Melanism is undoubtedly beneficial in environments where it leads to effective camouflage, or protection from harmful UV rays. According to wikipedia, melanism may even possibily increase disease resistance in cats (though it doesn't cite the source of this claim).

Nowhere does the creation.com article even attempt to explain why this mutation isnít advantageous. It simply starts with the assumption there are none and sticks with it regardless.

An even more compelling reason to dismiss this article as nonsense, which doesnít involve any debates over whether or not x mutation was beneficial, is the simple fact that point mutations have been observed to reserve in the laboratory. Base pairs in E. coli have been substituted Ė a mutation causing a phenotypic change Ė and then in later generations substituted back to the original pair - reversing this phenotypic change.

If either of these changes represent degeneration of the genome, then the reverse must represent an improvement. The claim that all mutations represent degeneration of the genome canít stand up to any further scrutiny.


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caffeine
Member
Posts: 1655
From: Prague, Czech Republic
Joined: 10-22-2008
Member Rating: 5.7


(2)
Message 160 of 210 (530594)
10-14-2009 6:37 AM
Reply to: Message 155 by Arphy
10-13-2009 6:13 AM


The timing of transitionals
Hello Arphy - there's a lot in this post to respond to, not all of which I feel qualified to do, but I did just want to address one quick point:

And then we have another bird fossil Confuciusornis sanctus initially dated at the same age as Archaeopteryx, yet it is clearly a bird and has beak as most birds have today. So what do we do? Do we shift Archaeopteryx foward,or sanctus back? But now we are just playing round with the facts to suit our purposes.

We don't need to move the fossils around in time, as this sort of thing is only a problem if we assume that all the fossils we discover must lie directly on the branch of some modern animal as it's direct ancestors, like so:

These fossils are supposed to represent clear transitionals. Fossil 1 shares traits with the modern animal, but not traits A, B or C. Fossil 2 shares the same traits, plus trait A, while Fossil 3 shares the same basic traits, plus both A and B.

The above picture would be in serious trouble if we discovered that Fossil 3 is actually quite a bit older than Fossil 2. This is only a problem, however, if we insist on drawing our family tree as a straight line. In the real world, it's spectacularly unlikely that the specific fossils we uncover will be the direct ancestors of today's animals - the vast majority of branches of the evolutionary tree end in dead ends. A more accurate picture might look like this (with time advancing from left to right):

Even though Fossil 3 is older than Fossil 2, it shares more traits with the living animal because their ancestry diverged more recently. Remember as well that there are scores more branches coming off this tree - I've just only included those which led to one of the fossils.

Transitional forms should rarely be expected to provide a clear line of descent from one to the other for the simple reason that most organisms leave no fossil trace. What they do show us is that intermediate forms sharing aspects of two groups did exist. While the line that led to Confuciusornis and modern birds lost their teeth, there was no requirement for other lines which left no descendants to also lose their teeth at the same time, and one of these led to Archaeopteryx.


This message is a reply to:
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