The Eurasian steppes, a wide expanse of grassland extending from the Black Sea to China, was home to varied populations of nomads, who appeared on the historical stage at the beginning of the first millennium B.C. Although the different confederations of nomads have varying names in historical writings, their cultures were strikingly uniform: a mobile way of life, based on migratory herding and horseback riding, with no major settlement; the bow and arrow as their main weapons; jewelry made of precious materials as symbols of power and status; a strong link with the animal world, expressed in their artistic production of small, portable objects with distinctive imagery of both real and fantastic animals, often in combat or intricately merged or entwined, referred to as "animal style"; and complex funerary practices, involving communal ceremonies and ritual sacrifices.
A nomadic lifestyle does not spur the writing of history, and study of such cultures is based mainly on archaeological evidence scattered from the Caucasus to China and on the preserved texts of the settled civilizations with which nomads interacted. The work of the fifth-century B.C. Greek historian Herodotos is the major written source of information on nomadic tribes who roamed the western reaches of the steppes from the seventh to third century B.C., called by the Greek with the collective name of Scythians. Similarly, Iranians used the broad nomenclature "Saka" for the nomads at their northwestern borders.
Chinese records discuss a confederation known as the Yuezhi who were pushed out of their territories on the northwestern frontier border by another group around 175 B.C. Some branches of the Yuezhi are known to have eventually settled in northern Afghanistan, and it has been suggested that the individuals buried at Tillya Tepe were members of the Yuezhi confederation. The Kushans (first century B.C. to third century A.D.