It's always interesting to see names that one knows. In this case, Dan Everett worked for the same organization, the Summer Institute of Linguistics, as I did, he in Brazil and my wife and I in Papua New Guinea (the main language we did literacy for wasn't anywhere near as complex as the Pirahă, but we did have 110 different endings for verb forms, including up to six at a time, in a specific order). I didn't know that Everett had left his faith behind. Another article that you also might find interesting is here. The other language mentioned, Banawá, was worked on by former friends (in that I haven't heard from them for years).
What is interesting in languages such as these is when families from outside are raised within the culture of the group. The children of linguists such as Everett and my friends the Bullers often learn to speak the languages quite well. Unfortunately when they, the children, return to the U.S. they become Third Culture Kids, and often have difficulties fitting in. This is in part why I returned with my family to the U.S., and why I (a lifelong pacifist) accepted my twin sons becoming Marines.