The Wari actually constructed enormous temples that served as collection points for mummies of people the Wari conquered. In a sense, they created penal colonies for the dead holding ancestors hostage to make the living obey. The Inca created a cult around the dead Inca royalty as divine ancestors of the sun. To the people of South America, death was not something different but a continued existence at a higher plane. Like the view of ancient Egyptians, they say death as something that continued life in a better world.
Humans also link between the living and supernatural in the form of ancestor worship.
This is particularly true of farming societies who often associated land with ancestry. They see the generations as a part of the cycles of nature. For the Andean cultures, life never ceased in a spiritual sense so from the Chinchorro culture to the Inca they kept the body of an ancestor with the living. To the Hopi, the dead become part of the cycle of death to the corn plant but leave seeds for new generations and bring rain as spirit essences to nourish the living. To the ancient mind reincarnation was a means to bridge the living directly with the cycles time and nature.