Neighbouring groups in Papua New Guinea had contact through intermarriage, trade and warfare, leading to a certain amount of bilingualism or competence in other dialects. A sizeable minority of New Guinean women have had the experience of being linguistic ‘foreigners’ in the village into which they have married.
‘We might well ask why such contacts did not lead to a lessening of linguistic differences. A partial explanation probably lies in the fact that New Guineans often make use of other-language and other-dialect knowledge in rhetoric and verbal art, highlighting the known differences between their own and neighbouring speech varieties. It appears that contacts with and awareness of other languages have led not to levelling but to heightened consciousness of and pride in difference.’
Gillian Sankoff, The social life of language (University of Pennsylvania Press, 1980) pp. 9-10, abridged
Quoted in Andrew Dalby, Dictionary of Languages (Columbia University Press, 1998) p. 491
Dalby points out that PNG “is linguistically the most complex region of the world. In mountainous, forested and swampy country, full of obstacles to travel, the languages of New Guinea have been developing and interacting for 40,000 years… It is a massive challenge to historical linguistics to trace language relationships that may date back 40,000 years or more. Genealogical trees have been drawn that link all the languages of New Guinea into a very few ‘phyla’, but for the present these all-embracing families are little more than blueprints for future research.”