It was a cold spring day, and the little boy had been out for too long, playing in the pond. The other members of the family were not paying much attention, and it was only with a start that the father first realized that the boy was no longer to be seen; then with a surge of anguished alarm he saw that not far from where the boy had been wading something was now floating. All attempts at resuscitation were futile. With great sadness they left the ambulance as the metal doors closed. Swiftly they made their way home, already late to prepare for the Sabbath. Young Adolf was dead.

To judge from the recurrent, if not increasing interest in counter-factual histories, be it the untimely demise of either tyrant or genius, the what-ifs of history seem to loom ever larger as the tapestry of events weaves folly compounded with stupidity, the witless leading the insane, to the soft applause of the flaccid and the time-server: ‘All loyal, my lord’. So many missed opportunities, such corruption and malice, laced with vaunting pride. All seems to be dependent on the twists and turns of fate, epitomized by the loose nail of the horse's shoe by which a kingdom is lost.

So, too, it is now widely thought that the history of life is little more than a contingent muddle punctuated by disastrous mass extinctions that in spelling the doom of one group so open the doors of opportunity to some other mob of lucky-chancers.