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Gaia

At 22:12 26/08/02 +1000, Ray wrote:
>Bill, I do not (of course) have any evidence for "Gaia", and although the
>Gaia Hypothesis, I have been duly informed :) was developed as an Earthbound
>idea which tied natural atmospheric cycles to a 'mind' of sorts, I stretch
>the idea beyond this small blue planet into the realms of carbonaceous
>chondrites and outer space as possible instruments for the evolution of
>life. (and should new ideas about Nanobes prove relevant, there too)

Ray, one of the problems with the Gaia Hypothesis is that is has varied meanings. The classical Gaia Hypothesis is so uncontroversial that I very much doubt you could find a serious biologist who would disagree with it.

The original Gaia Hypothesis, as put forward by James Lovelock, was simply that any planet on which life was established would have an atmosphere that was not in chemical equilibrium. Earth, for instance, has a large amount of oxygen that simply would not exist without the action of billions of years
of photosynthesis. So this basic version of Gaia is actually hard to disagree with -- sure there may be weird and obscure forms of life which don't do this, but it makes sense.

Lovelock muddied the water by then proposing another Gaia Hypothesis. His next proposal was that the Earth's ecosystem, since it maintained a chemical balance in the atmosphere, could be described as having
homeostatic properties. This is also uncontroversial.

Then he went further and proposed that the homeostatic properties of the planet's ecosystem made it arguable that the entire ecosystem was a sort of meta-organism. This is, of course, highly controversial and very few
scientists accept the full force of this argument.

Then Margulis muddied the waters even further by proposing that life evolved by *merging* branches as well as diverging branches. This was very controversial when she first proposed it, but now the evidence is
overwhelming that she was correct, and she won a Nobel Prize for her work. However, she also linked her theory to a sort of Nice and Fluffy view of evolution that was directly opposed to the Tooth and Claw school, and drew comparisons to the Gaia Hypothesis, thus giving the term yet another meaning.

And finally, beyond even the scope of Lovelock and Margulis, there are those who have elevated the meta-organism called Gaia to the level of a thinking, purposeful entity. This version of Gaia is quite clearly of
religious significance rather than scientific.

Whenever someone invokes Gaia, it is very difficult to know exactly what they mean.