The cosmic iceberg came in from the direction of the Sun, so no one saw its approach until the sky exploded. Seconds later, the shock wave flattened two thousand square kilometres of pine forest, and the loudest sound since the eruption of Krakatoa began to circle the world.

Had the cometary fragment been delayed a mere two hours on its age-long journey, the ten-megaton blast would have obliterated Moscow and changed the course of history.

The date was 30 June 1908.

It came in vertically, punching a hole ten kilometres wide through the atmosphere, generating temperatures so high that the air itself started to burn. When it hit the ground, rock turned to liquid and spread outwards in mountainous waves, not freezing until it had formed a crater two hundred kilometres across.

That was only the beginning of disaster; now the real tragedy began.

Nitric oxides rained from the air, turning the sea to acid. Clouds of soot from incinerated forests darkened the sky, hiding the sun for months. Worldwide, the temperature dropped precipitously, killing off most of the plants and animals that had survived the initial cataclysm. Though some species would linger on for millenia, the reign of the great reptiles was finally over.

The clock of evolution had been reset; the countdown to man had begun.