Explaining Global Patterns of Language Diversity

The six and a half thousand languages spoken by humankind are very unevenly distributed across the globe. Language diversity generally increases as one moves from the poles toward the equator and is very low in arid environments. Two belts of extremely high language diversity can be identified. One runs through West and Central Africa, while the other covers South and South-East Asia and the Pacific. Most of the world's languages are found in these two areas. This paper attempts to explain aspects of the global distribution of language diversity. It is proposed that a key factor influencing it has been climatic variability. Where the climate allows continuous food production throughout the year, small groups of people can be reliably self-sufficient and so populations fragment into many small languages. Where the variability of the climate is greater, the size of social network necessary for reliable subsistence is larger, and so languages tend to be more widespread. A regression analysis relating the number of languages spoken in the major tropical countries to the variability of their climates is performed and the results support the hypothesis. The geographical patterning of languages has, however, begun to be destroyed by the spread of Eurasian diseases, Eurasian people, and the world economy.