From: tkoenig@netcologne.de   
      
   Robert Woodward  schrieb:   
   > In article ,   
   >  Christian Weisgerber  wrote:   
   >   
   >> On 2025-12-17, Bobbie Sellers  wrote:   
   >>   
   >> >> BTW, where did this trope start?  It appears early in _Perry Rhodan_,   
   >> >> where genocidal wars between the two are part of the historical   
   >> >> background, but nothing is ever original in _PR_.   
   >> >   
   >> > 	Methane breathers in the Lensman stories by Doc E.E. Smith.   
   >>   
   >> I seem to recall that there were various "poison gas" breathers and   
   >> Smith was oddly unspecific about the makeup of their air.   
   >   
   > IIRC, there were Chlorine breathers in _Skylark of Valeron_. And a   
   > galactic empire of them in _Skylark Dequesne_.   
      
   How would these evolve?   
      
   Any kind of photosynthesis releasing Chlorine would   
   be... interesting.  It would probably have to start from HCl   
   instead of CO2, but hydrogen is not a good building block for   
   large molecules, you would have to get carbon from somewhere.   
   Plus, the acidity of HCl would vastly influence organic chemistry.   
      
   Hmm... has anybody ever tried to create an even quarter-plausible   
   handwaving biochemistry out of HCl/Cl2?   
      
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