Cave bears (left) would have been fearsome neighbours in the Stone Age — weighing up to a tonne or about 200 kg bigger than the modern heavyweights, the polar bear or the Kodiak bear.

But it turns out that they were largely vegetarian and went extinct earlier than expected as the Ice Age spread over Europe about 28,000 years ago.

Many of them apparently froze to death as they hibernated. Brrrr!  Or imagine waking up in spring to find a thick ice sheet has formed over the entrance to your cave home and trapped you inside.

So natural climate change wiped them out, rather than human hunters often blamed for killing them off about 13,000 years later, according to a study in the journal Boreas today.

Almost all extinctions since the Ice Age have been put down to human activities — and humans are now causing a global warming that U.N. studies say will cause the worst spate of extinctions since the dinosaurs vanished 65 million years ago.

 Another study this year suggested that climate change drove woolly mammoths to the brink of extinction about 6,000 years ago and then humans finished them off.

It’s reassuring to find cases like the cave bear where people weren’t to blame.

But can you think of many other examples?

(Picture of the cave bear courtesy of N. Frotzler, University of Vienna. Reuters News pictures of a Kodiak bear, above right, and of a polar bear, above left)