As a distinctive ethno-cultural region, Lithuania Minor emerged during the 16th or the 15th century. The substratum of the Prussian Lithuanian population comprised mostly ethnic Baltic tribes – either local (Old Prussians – Sambians, north Bartians, Natangians; either probably formerly Lithuanized or Prussian Scalovians and Nadruvians; Sudovians, some Curonians) or neighbouring (newcomers from the Grand Duchy of Lithuania: Lithuanians from the right side of the middle reaches of the Neman or Suvalkija, Samogitians, Sudovians, Prussians etc.). Colonists from the Holy Roman Empire also contributed to the Lithuanian population to some extent. Prussians and Yotvingians tended to be assimilated by Lithuanians in the northern part of East Prussia, and by Germans and Poles in the southern part.