Johann Friedrich Theodor Müller

Fritz Müller
Müller in Brazil
Born	31 March 1821 Windischholzhausen, Erfurt, Thuringia, Kingdom of Prussia
Died	21 May 1897 (aged 76) Blumenau, Brazil
Nationality	German
Fields	Biology
Alma mater	University of Berlin
Known for	Müllerian mimicry
Influences	Hermann Blumenau

Johann Friedrich Theodor Müller (31 March 1821 – 21 May 1897), better known as Fritz Müller, and also as Müller-Desterro, was a German biologist who emigrated to southern Brazil, where he lived in and near the German community of Blumenau, Santa Catarina. There he studied the natural history of the Atlantic forest south of São Paulo, and was an early advocate of Darwinism. He lived in Brazil for the rest of his life. Müllerian mimicry is named after him.

Müller was born in the village of Windischholzhausen, near Erfurt in Thuringia, Germany, the son of a minister. Müller had what would be seen today as a normal scientific education at the universities of Berlin (earning a BSc in Botany) and Greifswald, culminating in a doctoral degree in Biology. He subsequently decided to study medicine. As a medical student, he began to question religion and in 1846 became an atheist, joining the Free Congregations and supporting free love. Despite completing the course, he did not graduate because he refused to swear the graduation oath, which contained the phrase "so help me God and his sacred Gospel".

Müller was disappointed by the failure of the Prussian Revolution in 1848, and realised there might be implications for his life and career. As a result, he emigrated to South Brazil in 1852, with his brother August and their wives, to join Hermann Blumenau's new colony in the State of Santa Catarina. The colony, near the coast on the Itajaí River, was called Blumenau. In Brazil, Müller, living with his wife Caroline, became a farmer, doctor, teacher and biologist, sometimes employed by the provincial government, sometimes surviving on his own efforts, sometimes defending against Indians but always collecting evidence of life in the Atlantic forest. The climate here is sub-tropical, and the vegetation typical of the Brazilian coast: it is not rain forest.