Merritt Ruhlen ( /ˈmɛrɪt ˈruːlən/; born 1944) is an American linguist known for his work on the classification of languages and what this reveals about the origin and evolution of modern humans. Amongst other linguists, Ruhlen's work is recognized as standing outside the mainstream of comparative-historical linguistics. He is the principal advocate and defender of Joseph Greenberg's approach to language classification.