Though there are many ethnic and language groups that have or continue to live in the Andes and western South America, because of the similarities and long contact between them, we can think of them as one Andean civilization. Long before the growth of the Inka Empire, the diversity of climates prompted many indigenous communities to specialize and trade across regions and climates.
Water is scarce in many of the western Andean valleys and along much of the Pacific coast.
To overcome this scarcity, Indigenous communities organized large numbers of people, re-routed rivers and built elaborate irrigation systems. These systems greatly increased agricultural production and prompted the growth of kingdoms like that of Tiahuanaco or Wari. The frequency and density of trade increased and lead to widespread cultural exchange and the mass production of pottery and bronze. The Inkas borrowed and built upon the what they learned from other indigenous ethnic groups. Like the Romans borrowing from the Greeks, the Inkas took many of their religious beliefs from the Aymaras.