About the middle of the second millennium BC , Indo-Aryans began to move into and through the present area of Afghanistan. Much later came other tribal groups from Central Asia—Pactyes (from whom the present-day name "Pashtoons" derives), Sakas, Kushans, Hephthalites, and others—and a procession of Iranians and Greeks. In the 7th century AD , Arabs arrived from the south, spreading the new faith of Islam. In the same century, Turks moved in from the north, followed in the 13th century by Mongols, and, finally, in the 15th century by Turko-Mongols. This multiplicity of movements made Afghanistan a loose conglomeration of racial and linguistic groups.
All citizens are called Afghans, but the Pashtoons (the name may also be written as "Pushtun" or "Pukhtun," and in Pakistan as "Pathan") are often referred to as the "true Afghans." Numbering about 38% of the population in 2001, they are known to have centered in the Sulaiman range to the east; it is only in recent centuries that they moved into eastern and southern Afghanistan, where they now predominate. They have long been divided into two major divisions, the Durranis and the Ghilzais, each with its own tribes and subtribes.
The Tajiks, of Iranian stock, comprise nearly 25% of the population and are mainly concentrated in the north and northeast. In the central ranges are found the Hazaras (about 19%), who are said to have descended from the Mongols. To the north of the Hindu Kush, Turkic and Turko-Mongol groups were in the majority until 1940. Each of these groups is related to groups north of the Amu Darya and within the former USSR; among them are the Uzbeks, who number about 6% of the population. Other groups include the Aimaks, Farsiwans (Persians) and Brahiu. In the northeast are the Kafirs, or infidels. After their conversion to Islam at the end of the 19th century, they were given the name of Nuristanis, or "people of the light."