Brown Bear

## Evolutionary Timeline of the Brown Bear The brown bear (*Ursus arctos*) has a rich evolutionary history shaped by climatic shifts, particularly during the Ice Ages. Originating from ancient ursid ancestors, brown bears adapted to diverse environments across Eurasia and North America. Key environmental pressures included glacial cycles, which drove adaptations like increased body size, omnivorous diets, and hibernation behaviors. ### Key Milestones - **Late Miocene (about 10-5 million years ago)**: Emergence of early Ursus ancestors from primitive bears like *Ursavus*, adapting to forested habitats with changing climates. - **Pliocene (5-2.6 million years ago)**: Divergence of the Ursus genus, with species like *Ursus etruscus* appearing in Europe, facing warmer conditions and expanding grasslands. - **Early Pleistocene (2.6 million - 780,000 years ago)**: Brown bears evolve from *Ursus etruscus*, spreading across continents amid ice ages, developing larger sizes for cold survival. - **Late Pleistocene (780,000 - 11,700 years ago)**: Coexistence with cave bears (*Ursus spelaeus*), with brown bears adapting to post-glacial environments; human interactions begin. - **Holocene (11,700 years ago - present)**: Modern brown bears diversify into subspecies, influenced by human activities and habitat fragmentation.