It seems that, although there are signs of settlement in Peru earlier than 9000 BC, agriculture only became an important part of life in about 1000 BC, and even then only along the desert coast. Our knowledge of the Andean cultures is, however, very limited. We know that the Incas had developed into a high civilization only about 100 years before the arrival of Pizarro and his Spanish conquistadors, and we therefore do have written records of what they found. The Andean cultures, on the other hand, left no written records, only the knotted strings which probably allude to arithmetic records.
Historians have therefore to depend almost entirely on archaeological evidence.
Furthermore, we have no verbal record because the stories told to the Spaniards have been twisted to such a degree that within a single generation all Peruvian Indians came to believe that their culture stemmed solely from the Incas. What is clear from archaeological evidence is that the Incas, like their Meso-American counterparts, absorbed the relatively advanced culture already in existence at the time of their arrival. In fact, most of the Inca culture, especially building techniques, ceramics and the highly advanced bureaucratic state, were developments of earlier cultures. The Incas were therefore not a civilization but simply an empire within an already existing civilization. The Andean culture differed from the Meso-American variety in three specific ways.