Foundations of the Age-Area Hypothesis

The Age-Area Hypothesis (AAH) asserts that the point of geographical origin of a group of related cultures is most likely where the culture speaking the most divergent language is located. It is a crucial tool often used in piecing together the geographical origins of cultures. In spite of its widespread, multidisciplinary application, the hypothesis remains imprecisely stated, and has no theoretical underpinnings. I describe a model of the AAH based on an economic theory of mass migrations. The theory leads to a family of measures of cultural divergence, which I refer to as Dyen divergence measures after \citet{dyen56}. I use one measure to prove an Age-Area Theorem, which links linguistic divergence and likelihood of geographical origin. The theory allows for computation of the likelihood different locations are origin points for a group of related cultures, and can be applied recursively to yield probabilities of different historical migratory paths. The theory yields an Occam's-razor-like result: migratory paths that are the simplest are also the most likely; a key principle of the AAH. I conclude with an application to the geographical origins of the peoples speaking Semitic languages.