I did a ctrl-f in the article for "missionary" or "missionaries" and found nothing. There's a real problem (in my opinion) with weird evangelical Christian missionaries who treat the population of PNG as some sort of religious terra nullus. It's a bit weird to write a reasonably lengthy and detailed article about New Guinea and not mention the missionaries...?

They see it as some great holy mission from god to go out into the hinterlands and convert the local people from their local existing belief system to their own particular form of Christianity. The "mission aviation foundation" collects considerable amounts of money to operate bush planes for this purpose.

Edit: PNG is really the most egregious example, but there is clearly a phenomenon that exists of evangelical christian missionaries that seek out the "least developed" or most "bone in the nose" pre-technology isolated cultures and then do fervent work to convert them into dedicated followers of their own specific niche of Christianity. You'll see it in very rural parts of Africa as well. If you spend some time in the churches where they raise funds for these and look at the presentations of the guest speakers brought in to solicit funds for their ongoing missionary campaigns you'll know exactly what I'm talking about.