Travel 40 km (25 miles) in a straight line in New Guinea and the chances are you will have crossed a linguistic frontier: about 750 languages have been identified in New Guinea and its surrounding islands, and the linguistic map is far from complete. Whether you measure this figure against the area of the islands or their population, in either case it represents by far the greatest concentration of languages in the world. Applying New Guinea's ratio of one language per 1090 sq km (420 sq miles) to Britain would give that nation 211 different native tongues.
New Guinea, divided politically into Papua New Guinea and Irian Jaya (a province of Indonesia), has almost 5 million inhabitants, but many of these are recent immigrants. Only 3 million are speakers of the indigenous languages: an average of 4000 per language.
More than half of the languages are related, some very closely, and over 100 linguistic sub-families have been identified. Some languages are used by tribal groupings of 100,000 or more; others are spoken by just a few hundred or even a few dozen people, cut off in isolated valleys of the mountainous interior. There are almost certainly languages still to be classified, and in remote regions of Irian Jaya it is just possible that there are as yet undiscovered tribes.