How many languages?

[malloyd]

Originally Posted by dcarson

A mix of both I think. The valleys are separated by mountains that make travel slow and difficult. This is why Papua New Guinea has almost as many language families as the rest of the world. So the difference between valleys isn't French vs Italian but French vs Turkish.

Well usually more like French vs. Lithuanian. There seems to be fairly widespread agreement that more than half of them belong to a Trans New Guinea phylum.

But mountain valleys are good at this. Other places with a lot of diversity tend to be similarly mountainous but not too mountainous (presumably because it's hard to live on bare rock at all) - the Caucasus mountains, northwest California, the highlands from the eastern Himalayas down through central Indochina.