The only contact with the foreign Trailmen is through trade conducted once a year in silence and by sign language, since the isolated tribes are thought to have no common language.
John Okono, 28, came to the UK from Nigeria - an English-speaking country - three years ago and can see how some of the immigrant friends he has made have become isolated because of a lack of language skills.
In this isolated and impoverished area, where people cannot even speak the Indonesian national language, it is not hard to imagine separatist sentiments gaining a foothold again.