Brown bears are thought to have evolved from Ursus etruscus in Asia. The brown bear, per Kurten (1976), has been stated as "clearly derived from the Asian population of Ursus savini about 800,000 years ago; spread into Europe, to the New World. " A genetic analysis indicated that the brown bear lineage diverged from the cave bear species complex approximately 1. 2–1. 4 million years ago but did not clarify if U. savini persisted as a paraspecies for the brown bear before perishing. The oldest fossils positively identified as from this species occur in China from about 0. 5 million years ago. Brown bears entered Europe about 250,000 years ago, and North Africa shortly after. Brown bear remains from the Pleistocene period are common in the British Isles, where it is thought they might have outcompeted cave bears (Ursus spelaeus). The species entered Alaska 100,000 years ago, though they did not move south until 13,000 years ago. It is speculated that brown bears were unable to migrate south until the extinction of the much larger Arctodus simus.