Sixty-six million years ago, the Cretaceous period ended. Dinosaurs disappeared, along with around 90% of all species on Earth. The patterns and causes of this extinction have been debated since palaeontology began. Was it a slow, inevitable decline, or did the end come quickly, driven by a sudden, unpredictable disaster?
Georges Cuvier, working in the early 19th century, was one of the first palaeontologists. He believed that geological catastrophes, or “revolutions”, drove waves of sudden extinction. In part, his ideas were formed by study of a giant sea lizard, Mosasaurus, that lived and went extinct at the end of the Cretaceous.
Charles Darwin saw the end of the Cretaceous rather differently. He thought extinctions happened gradually, driven by everyday processes working over many millions of years, just as sedimentation and erosion slowly reshaped the land.
