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The Cambrian Larvae explosion?

 
 
Reply Sat 24 Sep, 2005 12:01 pm
DONALD I. WILLIAMSON Biologist, University of Liverpool; Author, The Origins of Larvae wrote:


Has anyone heard of this theory?

Does anyone know how well demonstrated this theory is?

Amazon link to his book.
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Acquiunk
 
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Reply Sat 24 Sep, 2005 12:18 pm
I do not know enough developmental biology to contribute a meaningful comment on this hypothesis but presumable the question could be answered through DNA analysis and an analysis of the chemical/genetic processes of transformation from larvae to adult stage.
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rosborne979
 
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Reply Sat 24 Sep, 2005 01:00 pm
Donald says that "none were larvae", referring to the fossils found in the Burgess shale.

How does he know that none were Larvae? Is there something that gives away a Larvae?

How do we know that Anomalocaris wasn't the larval form of something else? How do we know this about many things, like Trilobites or Crinoids for example. Dragonfly larvae don't look like adult dragon flies.
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farmerman
 
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Reply Sat 24 Sep, 2005 01:26 pm
Uh the Burgess shale came well after the "Cambrian Explosion" Im not sure about the "chimera" sequence.
The problem with this is that a "Cambrian Explosion" has been somewhat defused when , after much looking over fossil collections some scientists have determined that the pre CAmbrian life included less than 1% hard shell forms (Vendean animals) Early Cambrian , about 2 %, Late CAmbrian about 4% of species. If we look at it as a function of numbers of species rather than just pure numbers of specimens, the actual explosion was a bit more of an evolutionary advance. By the end of the PErmian we are at about 20% of all species being hard shelled or bony .

One of my students is doing an MS thesis on this very problem and shes working up available data freom the Walcott expedition and the fossils from Isua and Ediacara and another pC deposit from the Greenland and Canadian post Grenville strata.

Ill put her on this, I wont see her until November as shes doing her research now.
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DI Williamson
 
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Reply Sun 2 Oct, 2005 08:48 am
The Cambrian explosion
Darwin assumed that larvae and adults were part of the same genetic stock. My book (D.I.Williamson. 2003. The Origins of Larvae. Kluwer. Dordrecht) gives dozens of examples incompatible with Darwin's 'same stock' theory but consistent with my 'larval transfer' theory. This proposes that larval forms originated as adults in other taxa, and they were transferred by hybridization. Under this theory, larvae were later additions to the life-histories of animals. Sporadic hybridizations, however, have occurred in marine animals ever since the invention of sex. I claim that hybridizations between all sorts of ealy animals, before any of them had larvae, was the principal cause of the Cambrian explosion. This is explained more fully in my forthcoming paper, expected early 2006: D.I.Williamson. (in press). Animal evolution by higher taxa hybridization. Zoological Journal of the Linnean Society.
Don Williamson.
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DI Williamson
 
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Reply Sun 2 Oct, 2005 08:50 am
The Cambrian explosion
Darwin assumed that larvae and adults were part of the same genetic stock. My book (D.I.Williamson. 2003. The Origins of Larvae. Kluwer. Dordrecht) gives dozens of examples incompatible with Darwin's 'same stock' theory but consistent with my 'larval transfer' theory. This proposes that larval forms originated as adults in other taxa, and they were transferred by hybridization. Under this theory, larvae were later additions to the life-histories of animals. Sporadic hybridizations, however, have occurred in marine animals ever since the invention of sex. I claim that hybridizations between all sorts of ealy animals, before any of them had larvae, was the principal cause of the Cambrian explosion. This is explained more fully in my forthcoming paper, expected early 2006: D.I.Williamson. (in press). Animal evolution by higher taxa hybridization. Zoological Journal of the Linnean Society.
Don Williamson.
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farmerman
 
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Reply Sun 2 Oct, 2005 03:47 pm
hey welcome on board D.I.. Do you have any Vendean larvae/adult similarities?
Which species in the Burgess were you specifically studying?
I promise , Ill have your book in the department and be ready for some discussions for applied economic paleostratigraphy in Spring 06.
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rosborne979
 
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Reply Sun 2 Oct, 2005 04:18 pm
Re: The Cambrian explosion
D.I.Williamson wrote:
I claim that hybridizations between all sorts of ealy animals, before any of them had larvae, was the principal cause of the Cambrian explosion.


It's a very interesting idea. I like it, but I haven't heard much about it before.

I understand the idea that hybridizations may have lead to an increase in diversity, expecially back in the pre-cambrian when creatures were less specialized than they are today. But why do you add, "before any of them had larvae"?

How does the fact that something has larvae, or not, affect the idea of large scale hybridization?

Thanks, and welcome to A2K Smile
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