Humans arose ... as a fortuitous and contingent outcome of thousands of linked events, any one of which could have occurred differently and sent history on an alternative pathway that would not have led to consciousness.

No Geologist worth anything is permanently bound to a desk or laboratory, but the charming notion that true science can only be based on unbiased observation of nature in the raw is mythology. Creative work, in geology and anywhere else, is interaction and synthesis: half-baked ideas from a bar room, rocks in the field, chains of thought from lonely walks, numbers squeezed from rocks in a laboratory, numbers from a calculator riveted to a desk, fancy equipment usually malfunctioning on expensive ships, cheap equipment in the human cranium, arguments before a road cut.

I emphatically do not assert the general 'truth' of this philosophy of punctuational change. Any attempt to support the exclusive validity of such a grandiose notion would border on the nonsensical.

We must [it has been arued] go beyond reductionism to a holistic recognition that biology and culture interpenetrate in an inextricable manner.

Sure we fit. We wouldn't be here if we didn't. But the world wasn't made for us and it will endure without us.

But we all recognise the primary foible of frail humanity - our propensity for embracing hope and shunning logic, our tendency to believe what we desire rather than what we observe.

We have become, by the power of a glorious evolutionary accident called intelligence, the stewards of life's continuity on earth. We did not ask for this role, but we cannot abjure it. We may not be suited to it, but here we are.