Some of the first evidence of extensive human in-habitation on Bali dates back to approximately 2,500 B.C. The religion of the Bali Aga (original Balinese) centered around both Animism and Ancestor Worship. Ancestor Worship represents the belief that prosperity is associated with a relationship that exists between the living and the dead (prosperity is something that can only be achieved through intense worship and obtainment of blessings from ancestors). Animism represents the belief that inanimate objects and other elements of the natural landscape can possess souls which can help as well as hinder human efforts on Earth.
It remains a mystery as to whether or not the Bali Aga ever inhabited the site that is now known as the Sacred Monkey Forest of Padangtegal. Currently, there are only a few remaining Bali Aga villages on Bali and none of them are located in the vicinity of the Sacred Monkey Forest. However, today many Balinese believe that ravines and forested areas are particularly notorious for harboring human and animal spirits. These beliefs probably originated from the Bali Aga and suggest that the Bali Aga may have considered sites like Monkey Forest to be sacred.