Many of the people who played the natives were actual native South Americans who spoke little English. They were given free reign to say whatever lines they wanted, and it is rumored that in a couple scenes they're actually cursing up a storm.
The elderly priest sometimes seen traveling in the background is actually Daniel Berrigan, S.J. He is a well known Jesuit priest and professor who, along with his brother, is known for his work in human rights and social justice. He has one line in the film: He says "no".