Imagination plus dexterity, the ability to visualise what doesn't yet exist with the complementary ability to use materials at hand to bring it into existence. The secret of our evolutionary success.

But, like the animal that adapts to eat one particular type of food so well that it will starve if that food type vanishes, so we are over-evolved.

Our imagination didn't stop at simple tools, weapons and language. It swept us into cities, science, philosophy and the search for meanings and purposes which may well not exist.

We couild have done with a little less imagination.