Why Do Languages Diversify?

In the previous section I focused on the question of how language came about. But given that language evolved to allow information to be exchanged, why on earth do languages diversify so rapidly that they very quickly become mutually unintelligible? After all, there are now some 6,000 living languages, plus an untold number that have already become extinct. Within languages, dialects are equally diverse: until as late as the 1970s, a native English speaker dialect was sufficient to identify the speaker’s natal location to with 40 km. of his or her place of birth. Languages spawn dialects with unseemly speed, and dialects in turn eventually give rise to a new languages. Ancestral Indo-European, the language spoken by a small group of (probably Anatolian) agro-pastoralists around 6000 BC has given rise to around 150 descendant languages from Gaelic in the West to Bengali in the East over an 8000-year period. Interpolating these values into the standard Gaussian logistic growth equation for biological population growth suggests that the Indo-European language family has evolved at a rate equivalent to the budding off of a new language from each existing language, on average, about once every 1,600 years -- or about as long as it has taken modern English and Scots to evolve out of Anglo Saxon. ~ Page 230