That is a very good point. I should give you more credit, because the inspiration for this article came from one of your own (back in autumn).

The process of fossilisation is quite a tricky one. I was surprised to learn that in the tropics organisms don't fossilise readily because the decomposition is so fast and fierce.

I keep comming back to the conclusion that civilisations like ours must be rare indeed. I'm very much of the opinion that intelligent species stay connected to their home ecosystems (read Kim Stanley Robinson's book Aurora). We are all far to integrated into biosphere on this planet to survive independently.