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Author: LorenCobb Big gold star, 5000 posts Top Favorite Fools Top Recommended Fools Feste Award Nominee! Old School Fool Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: of 25027  
Subject: Re: Poll: First Life Form Date: 12/19/2012 11:35 AM
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I strongly doubt that the initial life form began with a self-replicating strand of RNA. It's too complex, and too delicate.

It seems very likely to me that the immediate precursor of life is a spherical membrane composed of a lipid bilayer (known since 1964 to arise spontaneously). Inside this protocol there would have to be a soup of chemicals capable of sustaining at least one autocatalytic reaction (these too are known to arise spontaneously).

en.wikipedia.org/wiki/Lipid_bilayer
en.wikipedia.org/wiki/Autocatalytic_reaction
en.wikipedia.org/wiki/Briggs-Rauscher_reaction

The next necessary step, I think, would be an ion pump mechanism that can preserve a chemical gradient between inside the membrane and outside. I am not certain about this, but I believe this too has been observed outside of any laboratory.

en.wikipedia.org/wiki/NaKATPase
www.nature.com/nature/journal/v481/n7381/full/nature10724.ht...

The change from autocatalytic to encoded reaction is one of degree, not of kind -- encoded reactions are just another form of autocatalysis. I doubt strongly that the first encodings were in RNA. Why make things so complex? It's only necessary to assume some very primitive and inefficient encoding. Evolution takes over from this point.

Energy flows are critical in these processes. That is one reason why I think the best current theory suggests that life may have begun in the extraordinarily energy-rich environment of undersea volcanic vents.

Martin & Russell (2003)
rstb.royalsocietypublishing.org/content/358/1429/59.short

Exactly where in this process did life begin? That may be an unanswerable and possibly meaningless question. It's like looking at the track of a tropical depression, and asking where, exactly, the hurricane emerged from the depression.

Loren
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