•August Schleicher (1821-1868): Schleicher indicated that contemporary languages had gone through a process in which simpler Ursprachen had given rise to descendent languages that obeyed natural laws of development. He argued that Darwin=s theory was thus perfectly applicable to languages and, indeed, that evolutionary theory itself was confirmed by the facts of language descent. "He regarded the three current language types, isolating, agglutinating, and infexional, as representing historical stages in the growth of languages to their highest point of organization. This conviction was expressed more than once in his statements that coexisting linguistic structural types represented the products of successive historical developments in the same way that successively evolved fishes, reptiles, birds, and mammals are represented today by coexistent species in our biological world" (Robins 1997:205).
•The Neogrammarians: A theory of linguistics that sought to explain language change in terms of sound laws without exception and postulated that modern irregularities in language were the result of past regular sound changes.
•Ferdinand de Saussure
•Charles Sanders Peirce