historians believe that the tajiks may be connected to ancient aryans who lived in the region for thousands of years. they were the heirs and transmitters of the central asian sedentary culture that diffused in prehistoric times from the iranian plateau into an area extending roughly from the caspian sea to the borders of china. the aryans constituted the core of the ancient population of khwarezm, sogdiana and bactria, which formed part of transoxania. they were included in the empires of persia and alexander the great, and they mixed with later invaders like the mauryans, kushans and hepthalites. over the course of time, the language that was used by these ancient people eventually gave way to farsi, a western dialect now officially spoken in iran, afghanistan and tajikistan. in the 13th century, genghis khan and his mongol army settled in many of the popular persian cities after wiping out the persian population. these mongols later adopted the persian language and the religion of islam, the persian-speaking hazaras claiming partial descent from them. tajiks usually reject a mongol or turkic origin and claim to be descended from the ancient iranians of central asia. however, historically, there has been heavy intermixing between the sedentary turkic-speaking central asians and the persian-speaking central asians