Comments: Ursus maritimus appears to share a common ancestor with the present-day grizzly/brown bear (Ursus arctos), branching off the brown bear lineage during the late Pleistocene (Amstrup 2003). Various evidence sources indicate these species are sister taxa, more closely related to each other than either is to the black bear (Ursus americanus); mtDNA sequences of brown bears from the Alexander Archipelago, southeast Alaska, were even found to be more closely related to mtDNA of polar bears than of other brown bears (Cronin et al. 1991). Cronin et al. (1991) found low divergence in mtDNA haplotypes among polar bear populations from Alaska and Canada.