Building the Comparative Method

August Schleicher first modeled language relationships as a family tree and produced an early systematic reconstruction of Proto-Indo-European, the method every later comparativist inherited.

Karl Verner refined the method by resolving a class of exceptions to Grimm's Law, showing that the position of the ancient accent, not chance, determined the outcome.

Franz Boas carried linguistic description across the Atlantic and into the field, arguing that variation among languages and cultures reflects history rather than a scale of progress.

Edward Sapir studied under Boas at Columbia, a course that redirected his career toward Native American languages and, later, toward the hypothesis that language shapes thought.

Otto Jespersen, working from Denmark, built the standard historical grammar of English and a theory of language change whose account of syntax Chomsky later credited as ahead of its time.

Joseph Greenberg extended comparison to the whole world's languages: his African classification is widely accepted, but the same method applied to the Americas produced the Amerind hypothesis most historical linguists reject, the clearest case of the method meeting its limit.