Present-day Iranians, or Persians, are considered to be direct descendants of the Aryans who moved into the plateau in the second millennium BC . They speak Persian, or Farsi, and number more than half the total population. In the Zagros range and its extensions are to be found the Kurds, Lurs, Bakhtiari, Qashqa'i, and Qajars; the first three are said to be of stock similar to the Iranian element, and they speak languages that stem from ancient Indo-European languages. At various times after the 10th century AD , Turkish tribes settled in the region, and Turkish-speaking groups are still found in several parts of the country. One-eighth of the total population dwells in East and West Azerbaijan, and there are sizable groups of Azerbaijanis in major cities elsewhere, including Tehran. Arab groups arrived during and after the 7th century AD ; their descendants live in the south and southwest and in scattered colonies elsewhere.
In general, non-Iranian elements are to be found along the perimeter of the country. Of these, certain nomadic groups move back and forth across the frontiers. Tribal groups have been a conspicuous element in Iran for many centuries, migrating vertically in spring and fall between high mountain valleys and hot, lowland plains. The important migratory groups include the Qashqa'i, Qajars, Bakhtiari, Balochi, and Turkmen. A large proportion of these people are now settled, however. The nomadic way of life is on the decline, and official policy has sought to resettle these groups on farmlands.
According to 1999 estimates, Persians account for 51% of the population, Azeri 24%, Gilaki and Mazandarani 8%, Kurd 7%, Arab 3%, Lur 2%, Balochi 2%, and Turkmen 2%.