Evidence for this... comes not ony from the archae
> bacterial domain. If one screens the entire tree of life
> for thermophiles, one tends to find them in the deepest
> branches" (though as the author points out this only takes
> us back to the last commmon ancestor)

TT
Which tells us the earth was bombed back into the dark ages
long ago by meteoric impacts - and the only things that survived
lived around deep undersea vents.

Interesting, perhaps - but rather irrelevant if you are trying
to look any further back than the last such event.

TH
But that brings up real problems. When do you
think life began?
This from a recent bio textbook:
"The more we learn about earth's early history
the more likely it seems that earth's first
organisms emerged and lived at very hot temp.
Rubble from the forming solar system slammed
into early earth from 4.6-3.8 bya, keeping
the surface molten hot.
As the bombardment slowed down, temp
dropped. By about 3.8 bya ocean temperatures
are thought to be dropped to a hot 49-88C."

That suggests for me that life IF started
between 3.8 or earlier was in a hot environment.
If not how do you explain the Issua evidence?
How do you explain the high Tm for RNA and
DNA. How do you explain life  starting up
so quickly. Also the bombardment was not
all or nothing. It would have been decreasing
in intensity throughout that period IMO.

I hope your answer is not panspermia, because
there is strong evidence against that too.
(And even if panspermia were true - and it is not -
the RNA would have to have been selected THERE -
wherever there could be - in a hot temp. So we're
back to square one.)

Comment?

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