For the traditional outlook of ancient Eastern Iran, the birthplace of Iranian culture, which must be guided by such realia as may be extracted from the religious texts which comprise the Avesta, supplemented, by Pahlavi citations from lost Avestan texts. The "Avesta people", like the Indo-Europeans who settled northwestern India and founded the Vedic culture, called themselves Arya. While our Avestan texts were composed at a period in which settled agricultural life had long before become widespread, the basis of social structuring it attests, which survived at least theoretically through Sasanian times, took shape during the earlier period of nomadism, and nomadic life has continued, of course, to exist side-by-side with agriculturism down to the present day in Iran. In the early stages of Indo-European thought, human fertility was connected with the concept of moisture and fluidity, and this association continued in the ancient Iranian outlook. The cattle-raising was a central part of the most ancient economy of Eastern Iran.