>Carbonaceous compounds found in sedimentary rocks were laid down by mats
>of
>photosynthetic organisms living in shallow seas 3.4 billion years ago,
>according to a paper in Nature this week.

I've been thinking about stromatolites, etc. (seemingly  some of the oldest
known life for sure so far), plus
articles like the one cited here,
And I notice a couple of things:

1. they live on shores, in shallow water. Note that is not the sea, and its not
the land. That suggests that first life may have needed both water (sea) and
sun (the dry shore).
2. There were microbes living off sunlight in shallow waters at 3.5 bya in NW
Australia in the Warrawoona region... These are photosynthesizers. Yet it would
have taken millions of years to reach that stage. That pushes the origin back
to around 4 bya or the era of the Hadrean - But note: the period (4-3.8) was
the time of the greatest Moon bombardment.
And  if the Isua , Greenland sample is correct at 3.75 bya, that too points to
an earlier origin, again in the bombardment phase and the hot phase of earth.

So three clues leap out at me.
1. Not all water, not all land, probably shore to get both water and sun. (a
sun/uv hot dry then cool wet cycle)
2. photosynthesizers at such an early date suggest to me that the sun/uv cycle
must have played a part IMO from the beginning  - I suggest it was the direct
cause of life.
3. the origin began in the hot Hadrean during the bombardment phase.

Comment?
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