RobertMaas{at}YahooGroups.Com wrote in news:c6opp7$1skn$1{at}darwin.ediacara.org:

>> From: "bw" 
>> I'm speaking of the niche of the "Archean
cyanobacteria".  Is there a
>> living cyanobacterium that lives in the same niche? Is there any
>> habitat (or microhabitat) that exists on earth today that is
>> indistinguishable, qualitatively, from that of 2 billion YA?  that
>> is, with the same temp, light, chemicals, anaerobic, etc.
> 
> There's one very important factor you didn't include in that list:
> Competition! For that one reason, no niche today is enough like any
> niche 2 billion years ago that an organism adapted to that old one
> could survive today, hence the genome has probably been forced to
> evolve a lot during the past 2 billion years even if the temperature
> etc. are all pretty much the same in some micro-environent near an
> undersea volcanic vent or whatever is the best match per only the
> physical parameters.

Well, I don't know about 2 billion years ago, but there are a number of 
bacteria, particularly chemoautotrophs, that are functioning at close to 
the theoretical limit in terms of extracting the available energy from the 
chemical reactions they carry out. Especially given that it is highly 
unlikely that any organism will develop a completely new biochemistry - 
i.e. they will be stuck with proteins,  DNA, the citric acid cycle, and 
phosphate bonds for carrying energy - there may not be any way for  
competition to take place, because there is no room for improvement in 
these very limited niches.
 

Yours,

Bill Morse
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