Surviving the Asteroid

66 million years ago, an asteroid 14 km in diameter hit the Earth. The cataclysm generated by the impact wiped out more than 75% of living species (flora and fauna). The dinosaurs, which had existed for 150 million years, were wiped out. No animal weighing more than 500 grams survived the catastrophe. On this earth strewn with ashes and debris, how did life find its way to renewal?