August Schleicher (February 19, 1821 - December 6, 1868) was a German linguist. His great work was A Compendium of the Comparative Grammar of the Indo-European Languages, in which he attempted to reconstruct Proto-Indo-European.
He began his career studying theology and Indo-European, especially Slavic languages. Influenced by Hegel, he formed the theory that a language is an organism, with periods of development, maturity, and decline. In 1850 Schleicher completed a monograph systematically describing the languages of Europe, Die Sprachen Europas in systematischer Übersicht (The languages of Europe in systematic perspective). He explicitly represented languages as perfectly natural organisms that could most conveniently be described using terms drawn from biology e.g., genus, species, and variety. Schleicher claimed that he himself had been convinced of the natural descent and competition of languages before he had read Darwin’s Origin of Species. He invented a system of language classification that resembled a botanical taxonomy, tracing groups of related languages and arranging them in a genealogical tree. His model, the Stammbaumtheorie (family-tree theory), was a major development in the study of Indo-European languages. He first introduced a graphic representation of a Stammbaum in articles published in 1853. By the time of the publication of his Deutsche Sprache (German language) (1860) he had begun to use trees to illustrate language descent. Schleicher is commonly recognized as the first linguist to portray language development using the figure of a tree. For the most part, however, Darwin’s ideas simply overlaid the fundamental features of Schleicher’s prior evolutionary project, which derived from the work of those individuals immersed in German romanticism and idealism especially Humboldt and Hegel.