To investigate the stability of ancient cave bear populations over time, the researchers obtained DNA samples from 29 cave bear teeth from three geographically close caves in the Ach Valley, near the Danube River in modern-day southern Germany. Twenty of the teeth ultimately provided useful mitochondrial DNA sequence (mitochondrial DNA is especially useful for tracking population changes). The findings indicated that while four sequence types (known as haplotypes) corresponded to bears 28,000 to 38,000 years old, a fifth DNA haplotype was found only in bears that were 28,000 years old or younger. These data suggested that what had been a stable, long-established cave bear population became disrupted around 28,000 years ago and was replaced by a new, genetically distinct cave bear group.
They suggest that shortly after the arrival of anatomically modern humans in the area, the local species left to be replaced by this new group. Don Grayson has done some work in France that suggests a possible link to certain cave bear extinctions and humans. Can't recall the actual place/dates off the top of my head though.