The only missionary I ever spoke to was a perfectly gogeous (Darn!) Italian priest, who worked with the Yanomamu in Brazil. His chief mission was to keep the Brazilian government from killing them off. Which struck me, at the time, as a worthwhile undertaking. He seemed to think they'd go to heaven if they were good Yanomamus. Eventually, they might become Catholics, but it would take a while, and he was more interested in keeping them alive than in converting them.
The Carnegie Museum uses his work on the Yanomamu culture.

Apparently the ladies of the University of Pittsburgh school of Anthropology went into a decline when they learned he was a priest. I do not blame them.