Asian civilizations were also on the rise. Also around 1500 BCE, the Shang dynasty began building their civilization along the Huang He (Yellow) River. Stratified by rank and occupation, the Shang were noted for casting magnificent bronze vessels for use in religious rites. Around 1029 BCE, they were succeeded by the Zhou. In order to justify overthrowing the Shang, the Zhou formulated what was known as "The Mandate of Heaven," the idea that a universal cosmic power bestowed right of rule. The Zhou expanded China's territory from the Huang He to the Yangtze valley, an area that became known as the Middle Kingdom. The Qin dynasty, founded by the emperor Shi Huangdi, spanned the years from 221-201 BCE. During Shi's consolidated reign, the Qin erected the Great Wall and extended China's border to Hong Kong and North Vietnam. The final dynasty of the Classical period was the Han, who continued Shi's centralized rule till around 220 CE, when waves of invasion began to weaken the country.
In the Americas, major cultures based primarily on agriculture had also formed during this time period. Two of the most complex and highly developed civilizations included the Olmec in Mesoamerica (present-day southern Mexico) and the Pueblo in what is now the southwestern United States. Mesoamerican cultures developed corn as a cultigen (a plant modified for human use, in this case teosinte grass). One of these Mesoamerican cultures, the Olmec, became the first major civilization in Mexico. They developed trading networks, built pyramids and large ceremonial centers, and produced giant stone heads. The Pueblo were noted for their cliff dwellings and pit houses sheltering hundreds to thousands of people, often situated around planned community spaces.
Other North American cultures included the Old Copper Complex in today's Great Lakes region, comprising societies which extracted copper for use in weaponry and ornament; the nomadic Hohokam in what is now Arizona; and the Norwood culture, noted for their fiber-based pottery, in what is now northern Florida.
During this period, most cultures were polytheistic, worshipping many gods. As the Bronze Age gave way to the Iron Age, elites and political leaders often encouraged the worship of one god, while still permitting belief in more than one god. This trend towards monotheism helped unify small nation-states. The foremost example of this trend was the exclusive god of Israel, Yahweh, whose worship in the form of Judaism would eventually give rise to Christianity. The two religions would have a profound effect on Western thought and political systems.
