How many mass extinctions have there been?

MASS EXTINCTIONS ARE A WIDESPREAD and rapid loss of life on Earth, typically in response to some kind of global catastrophe or change in climate. These events have occurred throughout Earth's history and have played pivotal roles in shaping both its past and current biodiversity.

- Will Newton

While they may be best known for destroying life, mass extinctions also promote the evolution of new species, levelling the playing field for groups who, prior to a mass extinction, may have lived in the shadows of more dominant species. Take mammals, for example - they prospered and rapidly diversified after non-avian dinosaurs were wiped out 66 million years ago. There have been five major mass extinction events. Together, these events are known as the 'big five'.

The Late Ordovician mass extinction, which took place 445 million years ago (MYA), wiped out 85 per cent of all species.