Re: [asa] lock-picking tools

From: David Campbell <>
Date: Mon Oct 20 2008 - 14:07:07 EDT

> For instance, we have excellent evidence now that there was no pre-biotic soup...the first signs of organicity in the oldest rocks were biotic, not pre-biotic. This was shown, I believe, with both carbon and nitrogen ratios. Just recently, an article was published that pushed the date for the oldest rocks from 3.86 back to about 3.9 BYA, and there *may* be signs of life there. When you look at that in the light of the Late Heavy Bombardment, the fact that fully developed cyanobacteria have been found in 3.86 byo rocks, what you are left with is an incredibly short time period for evolution to generate 1500 active genes, proteins, cell wall, etc. The best estimate I have run across is about 10 million years. But even if we make that 100 million years - do the math with the genetic material required. 100 MY is a tiny fragment of the time that is required, under GOOD conditions, for life to evolve.<

Actually, there are a number of uncertainties about a number of the
details. Rocks that old generally have major metamorphic alteration,
so interpreting exactly what was there at the formation is a problem
(even being absolutely sure which bits of rock are part of the really
old stuff and which are adjacent younger things is hard in some

Life is the best way we know of to create radical shifts in stable
isotope ratios for elements important in life (C, O, N, etc.).
However, there are inorganic processes that can create changes, too.

As we don't have older earth rocks, we can't conclude that there was
no prebiotic soup before the oldest rocks based on the content of the
rocks, though it might be possible to rule it out for some time
intervals if we can work out exactly when the entire earth was molten.
 (On the other hand, some organic synthesis could have taken place in
comets, etc. while the earth was unsuitable and then arrived via

Dr. David Campbell
425 Scientific Collections
University of Alabama
"I think of my happy condition, surrounded by acres of clams"
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Received on Mon Oct 20 14:07:43 2008

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