Why did so many languages develop in Europe?

1. Did many languages develop in Europe? Compared to many other areas of the world of comparable size--the North and South American continents, say, or India, or Australia--Europe is linguistically homogeneous. A single language family (Indo-European) dominates the continent, for instance, in the way that no language family dominates either America. 2. That said, Europe has greater language diversity than a mostly unilingual-English North America because it is a very large area with diverse ecological and geographical regions that has been inhabited for a long time. In the few thousands of years since speakers of Indo-European first appeared in the continent, under conditions of primitive travel and other technology, there was more than enough time for "Indo-European" to diversify into a vast collection of languages. The existence of non-Indo-European languages (Basque, Finnish, Estonian, Hungarian, et cetera) has as much to do with later migrations as with isolated survivals in variably marginal territories.

Europe? Have you looked at the Philippines? I'm pretty sure that the density of mutually-unintelligible languages there is a lot higher than in Europe, not to mention absolute numbers. Wikipedia: http://en.wikipedia.org/wiki/Languages_of_the_Philippines

To take one example: The Amish speak a German dialect because their religion originated in German-speaking parts of Europe.  But today a German and an Amishman trying to converse wouldn't be able to understand each other.  When speakers of a language are removed from their roots, that language tends to become very different. Europe is criss-crossed by mountains.  As European peoples spread out across the continent, they tended to put down roots rather than make difficult journeys back and forth across the mountains. Their languages evolved in one way in the places they left behind, and in different ways in their new homes.