The Azerbaijani are of mixed ethnic origin, the oldest element deriving from the indigenous population of eastern Transcaucasia and possibly from the Medians of northern Persia. Between the 3rd and 7th centuries CE there was a Persianization of the population, during the period of the Sassanian dynasty. A subsequent Turkification of the population occurred after the region’s conquest by the Seljuq Turks in the 11th century and a continued influx of Turkic peoples over subsequent centuries – including groups that migrated during the Mongol conquests of the 13th century (most of the tribes that formed the Mongol forces, or were led by them to migrate were Turkic peoples.)