Several paleontologists suggest the possibility of two separate brown bear migrations: inland brown bears, also known as grizzlies, are thought to stem from narrow-skulled bears which migrated from northern Siberia to central Alaska and the rest of the continent, while Kodiak bears descend from broad-skulled bears from Kamchatka, which colonized the Alaskan peninsula. Brown bear fossils discovered in Ontario, Ohio, Kentucky and Labrador show the species occurred farther east than indicated in historic records. In North America, two types of the subspecies Ursus arctos horribilis are generally recognized--the coastal brown bear and the inland grizzly bear; these two types broadly define the range of sizes of all brown bear subspecies.

Is it true that is a grizzly the same as a brown bear?
no