Although cultivation of crops has continued since the Neolithic, agriculture has always remained small in scale compared to pastoral nomadism. Agriculture may have first been introduced from the west or arose independently in the region. The population during the Copper Age has been described as mongoloid in the east of what is now Mongolia, and as europoid in the west. Tocharians (Yuezhi) and Scythians inhabited western Mongolia during the Bronze Age. The mummy of a Scythian warrior, which is believed to be about 2,500 years old, was a 30- to 40-year-old man with blond hair; it was found in the Altai, Mongolia. As equine nomadism was introduced into Mongolia, the political center of the Eurasian Steppe also shifted to Mongolia, where it remained until the 18th century CE. The intrusions of northern pastoralists (e.g. the Guifang, Shanrong, and Donghu) into China during the Shang dynasty (1600–1046 BC) and Zhou dynasty (1046–256 BC) presaged the age of nomadic empires.