Re: Not Hydrothermal Vents
From: TomHendricks474 (tomhendricks474_at_cs.com)
Date: 10/16/04
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Date: Sat, 16 Oct 2004 20:55:03 +0000 (UTC)
>> 1. For life to start it needs a consistent heat cycle
>> with enough variety to allow for variant results.
>> Hydrothermal vents are somewhat methodical, but
>> they would not have lasted the millions of years
>> necessary to form all the stages leading to life -
>> at least not in the same consistent way that the
>> sun could and did.
>>
>
>
>It's not unreasonable to assume that hydrothermal vents have been a constant
>
>feature on the earth since the formation of the oceans. They were certainly
>
>more plentiful when the earth was younger than today.
That is true, but the sun heat cycle has been more consistent over a longer
period - agreed? And the origin happened in a time where the Moon was much
closer, days as short as 5 hours (then 5 for night) and tides were horrendous.
This was no mild day at the beach. Also there was the age of bombardment - so
it is highly likely that any hydrothermal vent here this year would be gone the
next.
It is conceivable with lots of fluke factor that life could adjust to moving
vents, but why when the sun is overhead? Which would be easier to adapt to?
What does almost all life (except underground life) depend upon today if not
sunlight? And our oldest fossils show signs of photosynthesis so early on.
Why take a trip to Kenya when the 500 pound gorilla is right in front of us -
the sun.
Also note you may need not only a heat cycle, but a
dry/wet cycle - that would not be possible with hydrothermal vents.
TH (that Tom)
It's also reasonable
>
>to assume that zones of various states of heat and chemical composition
>
>throughout the oceans have also existed since that time. Currents were bound
>
>to keep any organisms well mixed throughout the ocean, moving from hotspot
>
>to hotspot, bringing genetic diversity to each one, creating a large and
>
>robust genepool.
>
>Hotspots are also a critical component of the "Snowball Earth" theory which
>
>presents evidence that earth was so cold from 1 billion to 500 million years
>
>ago, that the oceans were frozen to the bottom. During this time,
>hydrothermal vents would have been the critical oases of life that preserved
>
>it so that it could bloom in subsequent times.
>
>We do not know the complexity of the ecosystem that existed on the ocean
>
>floor at that time, but we do know that complex life began to flourish
>shortly afterwards. It's necessary that the prerequisite evolution was
>
>allowed to happen in the billions of years prior to the Precambrian period
>
>in some zone of the earth, and it's hard to think of a better candidate
>then
>the hydrothermal regions on the ocean floor.
>
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