From: Monte Davis 

Ellen K.  wrote:

>?

> GW >>So what?  We're part of "nature" too, dammit. 
The biggest ecological
>>disaster on the planet bar none was the evolution of photosynthesis and
>>the poisoning of the atmosphere with oxygen.

He's quite right. Oxygen -- like chlorine and fluorine -- is a highly
reactive gas that cheerfully rips apart many organic molecules. The
evidence indicates that for a good chunk of the earth's history, there
wasn't much of it around, and what there was got quickly bound up as CO2 or
in compounds with iron and other metals in the crust.

Then some organisms found very profitable (=energy-rich) biochemical
pathways that produced free oxygen as a nasty, corrosive waste product.
They flourished, dumping it into the atmosphere by the teraton -- which was
a disaster for most other organisms.

We, and every other animal, are descended from the oddball survivors that
developed a way to (1) protect our cells from the "poison" and
(2) turn it to use by eating carbon compounds from other living things and
"burning" them under tightly controlled conditions.

As Gary says, that's a crucial part of the earth's natural history. Let's
say that tomorrow an organism appears in the ocean with the ability to
metabolize chlorine ions (salt water, Na + Cl). It flourishes, giving off
growing clouds of a pale yellow-green gas that burns and poisons us. Gary,
of course, will welcome that as another facet of nature, and decry any
misguided attempt to interfere.

--- BBBS/NT v4.01 Flag-5