An exploding comet wiped out Stone-Age tribes, mammoths and other creatures in North America, scientists believe. The huge blast happened when a three-mile-wide space rock entered the Earth’s atmosphere over Canada nearly 13,000 years ago.

Researchers have found debris from the blast spread across the Earth from California to as far away as Belgium.

The buried clues include nanodiamonds, the rare element iridium and tiny balls of glass-like carbon formed in explosive conditions.

At one site in Arizona, the layers of comet debris were found to be covering mammoths that were being carved up by Stone Age butchers.

The scientists told the American Geophysical Union in Mexico that the exploding comet would have set off bush fires right across North America. They believe it could explain the disappearance of ancient tribe the Clovis people, plus giant beasts including mammoths and mastodons from the continent.

It also explains why elephants – descendants of the mammoth – are today found in Africa and Asia but not America.

In 1908 another, much smaller comet exploded over a remote part of Siberia. It flattened trees across 800 square miles around. An asteroid impact is believed to have wiped out the dinosaurs 65 million years ago. And last year, scientists reported the discovery of a crater beneath the Antarctic ice from an impact that wiped out nearly all life 250 million years ago.

An asteroid zipped past the Earth in March, proving that Earth is still in danger from cosmic collisions.

The photo is from an expedition to Tunguska in 1927, and shows trees flattened by the explosion 19 years earlier.

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