The pattern of lifeways established by the first millennium B.C. continues in North and Central Asia. Far to the north, tribes continue to live a hunting and gathering existence. On the northern steppe, with settled sites interspersed, nomadic groups herd their animals and form military alliances. These alliances often harass or conquer the settled populations to the south, east, and west, both before and after the Arab conquest of Central Asia. It is only at these times that the historical sources tell us much about them, although the nomadic populations are now literate and leave their own written records as well. The Hephthalites live on the western steppe; the Juan-juan and, later, Turkish tribes settle to the east. In the oasis areas further south, independent kingdoms rule in some areas while others are incorporated into the large empires at the borders: the Sasanian, Tang, and Umayyad and subsequent Muslim dynasties. Trade continues to play an important role in the wealth of Central Asian cities, where a rich mixture of cultures and languages thrive. The many religions of Central Asia, including Buddhism, Christianity, Judaism, Zoroastrianism, and Manichaeism, are eventually mostly supplanted by Islam. In the steppe and forest zones, traditional religions such as shamanism continue, and some groups practice Buddhism.