The rat is thought to have originated in the South-East Asia islands, India, central Asia and China before the Ice Age .
The world distribution of the rat was started by the shipping trade. The first to arrive in Europe was the black, or roof, rat, "Rattus rattus" around the 12th century. The larger, more aggressive, brown rat, "Rattus norvegicus", arrived during the 18th century.
The pet rat is belived to be a descendant of the brown rat, "Rattus norvegicus".