So it's not the sight of stromatolites that makes them exciting. It's the idea...

So it's not the sight of stromatolites that makes them exciting. It's the idea of them – and in this respect they are peerless. Well, imagine it. You are looking at living rocks – quietly functioning replicas of the very first organic structures ever to appear on earth. You are experiencing the world as it was 3.5 billion years ago – more than three-quarters of the way back to the moment of terrestrial creation. Now if that is not an exciting thought, I don't know what is. As the aforementioned palaeontologist Richard Fortey has put it: 'This is truly time travelling, and if the world were attuned to its real wonders this sight would be as well-known as the pyramids of Giza.' Quite right. Stromatolites are rather like corals in that all of their life is on the surface, and that most of what you are looking at is the dead mass of earlier generations. If you peer, you can sometimes see tiny bubbles of oxygen rising in streams from the formations. This is the stromatolite's only trick and it isn't much, but it is what made life as we know it possible. The bubbles are produced by primitive algae-like micro-organisms called cyanobacteria, which live on the surface of the rocks – about three billion of them to the square yard, to save you counting – each of them capturing a molecule of carbon dioxide and a tiny beat of energy from the sun and combining them to fuel its unimaginably modest ambitions to exist, to live. The byproduct of this very simple process is the faintest puff of oxygen. But get enough stromatolites respiring away over a long enough period and you can change the world. For two billion years this is all the life there was on earth, but in that time the stromatolites raised the oxygen level in the atmosphere to 20 per cent – enough to allow the development of other, more complex life forms: me, for instance. My gratitude was real. The

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