Our ancestors roaming in search of a shelter had to face a terrible adversary: the cave bear.

This beats was 30 % bigger than the brown bear (or grizzly, as is known in North America) and unlike the brown bear, was more akin to the cave habitat.

In just one cave, Pestera Ursilor (The Bear's Cave) in Romania, 140 skeletons were discovered.

Even if these bears lived along the Ice Age in Europe, 10,000 years ago they just vanished.

The climate change at the end of the last glaciation, with its changes in flora and fauna, was considered the cause for it, but this bear seemed to have gone extinct way before the glaciation ended, and a human role in the extinction was taken in account.

Now, researchers at Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, have made analyses of DNA achieved from fossil cave bear teeth, discovering a shift in the genetic pool of a particular population of the cave bears from the European last glaciation.

The DNA samples came from 20 cave bears discovered in three geographically proximate caves in the Ach Valley, close to the Danube River (southern Germany). The researchers investigated the mitochondrial DNA sequence (mitochondrial DNA can track population changes as it is transmitted strictly from mother to offspring).

Four DNA sequence types (haplotypes) matched bears 28,000 to 38,000 years old, while a fifth haplotype was discovered only in bears more recent than 28,000 years. This genetic pattern shows that a stable, old cave bear population vanished around 28,000 years ago and was replaced by another one, genetically distinct.

Fossil data point to the fact that the event occurred 28,000 years ago correlates with the entrance of modern humans in the Ach Valley, 32,000 years ago. Thus, modern humans, through direct hunting of the bears, competition for sheltering caves and food, could have eliminated the previous local population, creating space for the colonization with individuals from a neighboring population.

Even so, the new population stood up just another 2,000 years before disappearing.