RE: Documented evolution of new functions and behaviors in bacteria
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RE: Documented evolution of new functions and behaviors... - 12/9/2008 12:16:01 PM
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Bettawrekonize
Posts: 1177
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quote:
ORIGINAL: alex123
One current proposal is that the apparently rapid divergence in the early Cambrian is caused by the evolution of the ability to generate hard body parts (tough proteins, calcite, carbonates, etc) that were much more easily fossilised.
Speculation. This is just an attempt to explain the lack of evidence for the slow divergence of life. Since there is no evidence that life diverged slowly, instead of accepting the evidence for what it says, this argument tries to explain why the evidence is lacking. No matter what the evidence (regardless of whether or not the fossil record shows that life diverged slowly), it's evidence for evolution, further demonstrating the unfalsifiable nature of evolution.
Has anyone ever observed the evolution of the ability to generate hard body parts (without human intervention causing such a thing), or is just more speculation?
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This would mean that the Cambrian does not reflect an explosion so much as the 'disclosure' of an existing diversification.
Since there is no evidence of this, there is no reason for me to believe this.
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RE: Documented evolution of new functions and behaviors... - 12/10/2008 7:49:23 AM
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alex123
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<snip>There is quite a nice summary of the Cambrian at http://www.fossilmuseum.net/Paleobiology/CambrianExplosion.htm
Actually, this isn't true at all; there exists quite a bit of evidence that the Cambrian explosion occurred (indeed, that is the standard understanding in paleontology)
True, it is the standard understanding, but it is increasingly being questioned as new evidence is uncovered
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as your own link acknowledges at the beginning:
Most major animal groups appear for the first time in the fossil record some 545 million years ago on the geological time scale in a relatively short period of time known as the Cambrian explosion.
They certainly seem to appear at that time but there is considerable evidence (both palaeontological and genetic) that they were there earlier in a less visible form and therefore their appearance was not quite as sudden as it might appear.
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Indeed, there exists significant genetic evidence that the diversification of of major animal phyla in the genetic record as well.
I couldn't get your link to work! (I couldn't even get the pasted link to work either!)
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In addition, the Cambrian explosion wasn't the only 'explosion' of diversity in earth's past - the was the Avalon explosion, an explosion of major flowering plants, beetle types, etc.
The 'Avalon' explosion was the emergence of the preCambrian Ediacaran fauna, not flowering plants, etc. ( http://www.sciencedaily.com/releases/2008/01/080103144451.htm)
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Rapid genetic diversification seems fairly certain - and the the arguments against it, for example that major genetic complexity is far older really don't contradict the occurence of such an explosion, in fact they make the gradual development of genetic complexity less likely.
I agree with your first statement up to a point, but I don't think that the Cambrian represents the 'face value' explosion of form that has been claimed. There certainly seem to have been periods of rapid expansion in the fossil record but I don't think that the concept of a (geologically) instant explosion from 3 to 30+ metazoan body forms at the start of the Cambrian is borne out by the increasingly detailed examination of the evidence.
As for 'making the gradual development of genetic complexity less likely', I dont think that that follows at all.
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RE: Documented evolution of new functions and behaviors... - 12/10/2008 12:03:46 PM
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Jhud
Posts: 4661
Joined: 4/11/2005
From: Lake Wobegon
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quote:
They certainly seem to appear at that time but there is considerable evidence (both palaeontological and genetic) that they were there earlier in a less visible form and therefore their appearance was not quite as sudden as it might appear.
I think speculating about 'less visible' forms doesn't help so much here. In fact, there were forms that existed before the Cambrian, and they represent an explosion of life as well, during the Avalon explosion, though these forms don't seem to presage the Cambrian forms (which are really the modern forms) at all.
And the link I provided (which seem to work fine for me - http://www.sciencemag.org/cgi/content/full/310/5756/1933) details how the genetic evidence mirrors an understanding of a rapidly radiating animal forms.
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The 'Avalon' explosion was the emergence of the preCambrian Ediacaran fauna, not flowering plants, etc. ( http://www.sciencedaily.com/releases/2008/01/080103144451.htm)
I know what the Avalon explosion is - you read it wrong - each of those groups was marked by an explosion of rapidly radiating forms.
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I agree with your first statement up to a point, but I don't think that the Cambrian represents the 'face value' explosion of form that has been claimed. There certainly seem to have been periods of rapid expansion in the fossil record but I don't think that the concept of a (geologically) instant explosion from 3 to 30+ metazoan body forms at the start of the Cambrian is borne out by the increasingly detailed examination of the evidence.
As for 'making the gradual development of genetic complexity less likely', I dont think that that follows at all.
Actually, up to now most of the 'evidence' you have presented has either been speculative, or made the case worse by pushing genetic complexity back further in time, giving less time for such diverse forms to develop evolutionarily.
But in a way it doesn't matter; we know now the basic genetic information is very ancient, conserved, anticipatory, and did not develop by cumalitive additional means.
_____________________________
Jack
I believe in Christianity as I believe that the sun has risen: not only because I see it, but because by it I see everything else.
- C.S. Lewis
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RE: Documented evolution of new functions and behaviors... - 12/11/2008 1:29:58 PM
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GHitch
Posts: 1007
Joined: 7/6/2008
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Actually, up to now most of the 'evidence' you have presented has either been speculative, or made the case worse by pushing genetic complexity back further in time, giving less time for such diverse forms to develop evolutionarily.
But in a way it doesn't matter; we know now the basic genetic information is very ancient, conserved, anticipatory, and did not develop by cumalitive additional means. Indeed. Your first point always seems to be true in these debates. And the 2nd is, imo anyway, indisputable. DNA has been the center of the picture since the beginning.
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It is an algorithm that lies at the humming heart of life, ferrying information from one set of symbols (the nucleic acids) to another (the proteins). An algorithm? How else to describe the intricacy of transcription, translation, and replication than by an appeal to an algorithm? For that matter, what else to call the quantity stored in the macromolecules than information?
...
Using very simple counting arguments, Hubert Yockey has concluded that an ancient protein such as "cytochrome c" [see the latest posts in the Origin of species thread] could be expected to arise by chance only once in 10<44> trials. The image of an indefatigable but hopelessly muddled universe trying throughout all eternity to create a single biological molecule is very sobering. It is this image that, no doubt, accounted for Francis Crick's suggestion that life did not originate on earth at all, but was sent here from outer space, a wonderful example of an intellectual operation known generally as fog displacement.
- Berlinski - The End of Materialist Science Subject: Anti-Evolution Articles - Date: 12/2/1996
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"The success of Darwinism was accompanied by a decline in scientific integrity. ...To establish the continuity required by the theory, historical arguments are invoked even though historical evidence is lacking." -W. R. Thompson, PhD
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