I am the furthest possible thing from a linguist but looking at a hastily searched language map of PNG, my first thought is "wow, that's a lot. And some of those aren't even in the same family of language?"

https://upload.wikimedia.org/wikipedia/commons/f/f6/TNG_map....

> wow, that's a lot. And some of those aren't even in the same family of language?

Indeed! Palmer counts ‘862 languages comprising 43 distinct families […] and 37 isolates’, (where an isolate is a language with no known relationship to any other family). I should add that the map you linked shows the branches of only a single language family, namely Trans–New Guinea — most of the other 42 families are in the grey areas. (Though due to uncertainties in historical linguistics, that map includes some groups as part of Trans–New Guinea which Palmer considers separate families, for instance Timor—Alor–Pantar [there part of ‘West Trans–New Guinea’] and South Bird’s Head.)