This is from Everett’s book, Don’t Sleep, There are Snakes: Life and Language in the Amazonian Jungle:
Perhaps the activity closest to ritual among the Pirahãs is their dancing. Dances bring the village together. They are often marked by promiscuity, fun, laughing, and merriment by the entire village. There are no musical instruments involved, only singing, clapping, and stomping of feet. …]
Pirahãs have told me about a dance in which live venomous snakes are used, though I have never seen one of those (such dances were corroborated, however, by the eyewitness account of the Apurinã inhabitants of Ponto Sete, before the Pirahãs dispersed them). In this dance, the regular dancing is preceded by the appearance of a man wearing only a headband of buriti palm and a waistband, with streamers, made entirely of narrow, yellow paxiuba palm leaves. The Pirahã man so dressed claims to be Xaitoií, a (usually) evil spirit whose name means “long tooth.” The man comes out of the jungle into the clearing where the others are gathered to dance and tells his audience that he is strong, unafraid of snakes, and then tells them about where he lives in the jungle, and what he has been doing that day. This is all sung. As he sings, he tosses snakes at the feet of his audience, who all scramble away quickly.
These spirits appear in dances in which the man playing the role of the spirit claims to have encountered that spirit and claims to be possessed by that spirit. Pirahã spirits all have names and personalities, and their behavior is somewhat predictable. Such dances might be classified as a weak form of ritual, in the sense that they are witnessed and imitated and clearly have value and meaning to the community. As ritual they are intended to teach the people to be strong, to know their environment, and so on.
The relative lack of ritual among the Pirahãs is predicted by the immediacy of experience principle. This principle states that formulaic language and actions (rituals) that involve reference to nonwitnessed events are avoided. So a ritual where the principal character could not claim to have seen what he or she was enacting would be prohibited. Beyond this prohibitive feature, however, the idea behind the principle is that the Pirahãs avoid formulaic encodings of values and instead transmit values and information via actions and words that are original in composition with the person acting or speaking, that have been witnessed by this person, or that have been told to this person by a witness. So traditional oral literature and rituals have no place.
If you read Everett’s book (even in places), you’ll notice that the spirits do occupy a place in Pirahã society: they trade names with the Pirahã from time to time, they can tell the village what it shouldn’t have done or what it shouldn’t do, they can appear in dreams (dreams in Pirahã thinking are classified as real experiences - they are not just figments of the imagination. You see one way awake and another while asleep, and both are considered to be ‘real’), and the Pirahã claim to see them.
I think the ‘problems’ Everett encountered is more due to the fact that the Western version of Christianity is pretty much centered on concepts that are foreign to the Pirahã: history (things that happened ‘in the past’), oral tradition, and a lesser emphasis on ‘seeing is believing’ (“Blessed are those who have not seen yet believed”). The Pirahã value direct experience over abstract concepts, actual eyewitnesses, and the ‘now’.