Bears have fascinated people since ancient times. The relationship between bears and humans dates back tens of thousands of years, during which time we have also competed with bears for shelter and food. Our strong link with bears is also attested to by the Neanderthal burial of “Le Regourdou,” in France, where the skeleton of a Neanderthal in a fetal position was found under a funeral slab surrounded by the bones of a brown bear, probably sacrificed for the burial. Bears were also represented in rock paintings in caves inhabited by our ancestors in Europe. The bears depicted by our ancestors were cave bears, which roamed Eurasia until about 24,000 years ago when they became extinct during the Last Glacial Maximum. Recently, gene flow between extinct cave bears and brown bears has been discovered, providing direct evidence for ancestral hybridization between the two species which resulted in the modern Ursus arctos that we all know (Chapter 1).