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The huge cave bears that once roamed Europe started to disappear just after modern humans arrived. The finding from a new genetic analysis suggests that our ancestors played a big role in driving the bears to extinction.

Cave bears (Ursus spelaeus) are the clearest example of ancient humans wiping out a large-bodied species, at least in Europe, says Verena Sch眉nemann at the University of Zurich in Switzerland.

The bears roamed Europe for over 100,000 years. They were as large as modern grizzly bears and ate mostly plants. Many fossils have been found in caves, suggesting they spent a lot of time there 鈥� perhaps hibernating.

They died out around 26,000 years ago. This was the Last Glacial Maximum, when the most recent ice age reached its peak and ice sheets extended far south. Some researchers interpreted this to mean that the cooling climate killed them off.

To find out what really happened, Sch眉nemann and her colleagues sequenced DNA from 59 cave bears. They focused on mitochondrial DNA, which is only inherited from the mother. In addition, they examined 64 mitochondrial DNA sequences that had already been published.

The new genetic data provides 鈥渁 much better view of the diversity,鈥� says Sch眉nemann. Her team found that there were five major lineages of cave bears dotted around Europe. But聽40,000 years ago, their genetic diversity fell dramatically, suggesting the number of cave bears was declining. 鈥淭here are still a few around, but there is this massive loss of diversity,鈥� says Sch眉nemann.

Cave snatchers

The cave bear decline happened just as modern humans began spreading through Europe in a big way, replacing the Neanderthals that had lived alongside the bears for millennia. That suggests humans were at least partly responsible.

Humans may not have directly killed many cave bears, says Sch眉nemann. Instead they probably took their caves. The bears tended to live near their birthplace, so if humans took over their caves they would have found themselves homeless. Furthermore, their home caves were typically surrounded by plants they could eat. 鈥淚f they lose that, they also lose their feeding possibilities,鈥� says Sch眉nemann.

With their population smaller, the Last Glacial Maximum would then have finished off the cave bears. 鈥淭hey might have survived if there wasn鈥檛 this decline before,鈥� says Sch眉nemann. Cave bears had come through similarly cold periods before.