Mamooth Extinction Story Retold

The controversial idea that space impacts may have wiped out woolly mammoths and early human settlers in North America has received new impetus.

Nano-diamonds and other exotic impact materials have been unearthed in thin sediments, Science magazine reports.

The age of these materials coincides with the start of a millennium-long climate cooling event known as the Younger Dryas - some 13,000 years ago.

Many large animals vanish from the archaeological record at this time.

It is also the period in Earth history that sees the demise of Clovis culture - the prehistoric civilisation that many regard as the first human occupation of North America.

Taken together, it all makes for a compelling story, claims the team behind the latest research.

Question of origin

The group used transmission electron microscopy (TEM) to identify tiny impact diamonds found at a range of sites - four of them Clovis archaeological digs - across North America. Diamonds form through intense pressure and heat.

"We've discovered nano-diamonds that are not normally produced through average processes on the surface of the Earth," said James Kennett, a geologist at the University of California, Santa Barbara, and author on the Science paper.

"They indicate there was an extra-terrestrial event on Earth 12,900 years ago,"