What an odd time to be a fundamentalist about adaptation and natural selection - when each major subdiscipline of evolutionary biology has been discovering other mechanisms as adjuncts to selection's centrality.

Life began three and a half billion years ago, necessarily about as simple as it could be, because life arose spontaneously from the organic compounds in the primeval oceans.

The myriad valleys could have arisen anywhere on the landscape. The current positions are quite accidental. If we could repeat the experiment, we might obtain no valleys at all, or a completely different system. Yet we now stand at the shore line contemplating the fine spacing of valleys and their even contact with the sea. How easy it is to be misled and to assume that no other landscape could possibly have arisen.

Wind back the tape of life to the early days of the Burgess Shale; let it play again from an identical starting point, and the chance becomes vanishingly small that anything like human intelligence would grace the replay.

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.

With copious evidence ranging from Plato's haughtiness to Beethoven's tirades, we may conclude that the most brilliant people of history tend to be a prickly lot.

No one-liner can ever be optimal.