The master race (, ) was a concept in Nazi ideology in which the Nordic race—a branch of what in late-nineteenth and early-twentieth century taxonomy was called the Aryan race—represented an ideal and pure race. In Nazi ideology, the Nordic race was the purest example of the original racial stock of those who were then called the Proto-Aryans, whom the Nazis believed to have prehistorically dwelt on the North German Plain and to have ultimately originated from the lost continent of Atlantis. The Nazis declared that the Nordics (now referred to as the Germanic peoples), were the true Aryans (ethnically closest descendants of the Proto-Indo-Europeans) because they were much less racially mixed with peoples who were "non-native" to the European continent, than other Indo-European peoples, such as the Slavic peoples, the Romanic peoples, and the Indo-Iranian peoples. Based on this claim that the Nordic peoples were superior to all other races, the Nazis believed they were entitled to expand territorially. This concept is known as Nordicism. The actual policy that was implemented by the Nazis resulted in the Aryan certificate, the one form of the official document that was required by the law for all citizens of the Reich was the "Lesser Aryan certificate" (Kleiner Ariernachweis) which could be obtained through an Ahnenpass which required the owner to trace their lineage through baptism or birth certificates or certified proof thereof that all grandparents were of "Aryan descent".