That seems to be the conclusion of a mostly European research:
Mathias Stiller et al. Withering Away—25,000 Years of Genetic Decline Preceded Cave Bear Extinction. Molecular Biology and Evolution 2010. Pay per view.
The causes of the late Pleistocene megafaunal extinctions are still enigmatic. Although the fossil record can provide approximations for when a species went extinct, the timing of its disappearance alone cannot resolve the causes and mode of the decline preceding its extinction. However, ancient DNA analyses can reveal population size changes over time and narrow down potential causes of extinction. Here, we present an ancient DNA study comparing late Pleistocene population dynamics of two closely related species, cave and brown bears. We found that the decline of cave bears started approximately 25,000 years before their extinction, whereas brown bear population size remained constant. We conclude that neither the effects of climate change nor human hunting alone can be responsible for the decline of the cave bear and suggest that a complex of factors including human competition for cave sites lead to the cave bear's extinction.
Cave bears went extinct roughly at the time of the Last Glacial Maximum, 25-18,000 years ago.
· Article at Science Daily
· Leherensuge: Mammoths died because of forest expansion.