The preceding Palaeocene epoch was also brought to an end, the rocks suggest, by a sudden release of methane.

ECONOMIST: A geological burp may have led to the dinosaurs�� domination

The characteristic Palaeocene fauna seems to have come and gone with the ancestors of modern mammals still skulking unchanged in their burrows.

ECONOMIST: Rewriting the history of the mammals

It was during the Eocene, which began 56m years ago, following the Palaeocene, that the ancestors of mammals around today are supposed to have diversified.

ECONOMIST: Rewriting the history of the mammals

As to what happened to the Palaeocene fauna, the evidence points not towards an errant asteroid but to a giant burp from the oceans, which released a huge amount of methane.

ECONOMIST: Rewriting the history of the mammals