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qetzal



Posts: 311
Joined: Feb. 2006

(Permalink) Posted: Nov. 16 2011,11:26   

Quote (Dr.GH @ Nov. 16 2011,07:07)
 
Quote (midwifetoad @ Nov. 16 2011,00:24)
Shapiro plays at  being L'enfant terrible, but he doesn't seem stupid enough to assert that variation anticipates need.

He seems to take an extreme position on evolvability and seems to assert that there are mechanisms to increase certain kinds of mutations as a response to stress.

There are in bacteria. Under heat stress, or antibiotic attack, error checking during DNA replication is turned (nearly) off in bacteria (and archaea?) generating huge mutation rates.

This could be why bacteria are so successful. But, this approach would obviously destroy any metazoans.

There are certainly mechanisms that increase mutation rates under stress. But is there evidence that such increased mutation is actually adaptive? Or is it merely an unavoidable consequence of things like needing to relax proofreading in order to replicate damaged DNA?

Shapiro definitely thinks it's adaptive. He even goes so far as to claim that:

 
Quote
Large-scale genome-wide reorganizations occur rapidly (potentially within a single generation) following activation of natural genetic engineering systems in response to a major evolutionary challenge. The cellular regulation of natural genetic engineering automatically imposes a punctuated tempo on the process of evolutionary change.


This does seem to flirt with ideas like front loading and purposeful evolution. Perhaps he's merely being excessively metaphorical, but I don't see any sense in which individual organisms can be properly described as responding to evolutionary challenge.

He also ignores the seemingly insurmountable issue of how such mechanisms could apply to large organisms. Individual cells in our bodies might respond to stress in some of the ways Shapiro suggests, but there's no known mechanism to allow "successful" responses in a somatic cell to be transmitted to the germ cells.

  
  366 replies since Nov. 08 2011,06:46 < Next Oldest | Next Newest >  

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