Andean is a regional label, not a people. The sequence runs from Chavin de Huantar in the first millennium BCE, whose sunken plaza and underground galleries drew visitors from a wide area, through Moche and Nazca on the coast, Tiwanaku on Lake Titicaca and Wari in the highlands, to the Inca state that absorbed most of it, and on to the Quechua and Aymara communities who are its living continuation.
What holds the sequence together is a set of practices rather than a single ancestry: terraced agriculture at altitude, the use of many ecological zones by one community, camelid herding, and the treatment of the dead as continuing members of the group who are fed, dressed and consulted. The khipu, records made of knotted cords, are the region's distinctive administrative technology. Gary Urton's analysis of their binary features shows a system capable of far more than accountancy, and whether some khipu encode narrative rather than number remains an open question.
Alphabetic writing arrived with the Spanish, so nearly every early written account of Andean religion was produced by or for the people dismantling it. The extirpation records are detailed precisely because they were investigations, and they remain a principal source. Reading them requires holding both facts at once, because they preserve what they were compiled to destroy.