Jean Louis Rodolphe Agassiz (May 28, 1807 – December 14, 1873) was a paleontologist, glaciologist, geologist and a prominent innovator in the study of the Earth's natural history. He grew up in Switzerland and became a professor of natural history at University of Neuchâtel. Later, he accepted a professorship at Harvard University in the United States.
Louis Agassiz was born in Môtier (now part of Haut-Vully) in the canton of Fribourg, Switzerland. Educated first at home, then spending four years of secondary school in Bienne, he completed his elementary studies in Lausanne. Having adopted medicine as his profession, he studied successively at the universities of Zürich, Heidelberg and Munich; while there he extended his knowledge of natural history, especially of botany. In 1829 he received the degree of Doctor of Philosophy at Erlangen, and in 1830 that of doctor of medicine at Munich. Moving to Paris he fell under the tutelage of Alexander von Humboldt and Georges Cuvier, who launched him on his careers of geology and zoology respectively. Previously he had not paid special attention to the study of ichthyology, but it soon became the great focus of his life's work.
In 1819–1820, Johann Baptist von Spix and Carl Friedrich Philipp von Martius were engaged in an expedition to Brazil, and on their return to Europe, amongst other collections of natural objects they brought home an important set of the fresh water fish of Brazil, and especially of the Amazon River. Spix, who died in 1826, did not live long enough to work out the history of these fish, and Agassiz (though fresh out of school) was selected by Martius for this purpose. He at once threw himself into the work with an enthusiasm which characterized him to the end of his busy life. The task of describing the Brazilian fish was completed and published in 1829. This was followed by research into the history of the fish found in Lake Neuchâtel. Enlarging his plans, in 1830 he issued a prospectus of a History of the Freshwater Fish of Central Europe. It was only in 1839, however, that the first part of this publication appeared, and it was completed in 1842. In 1832 he was appointed professor of natural history in the University of Neuchâtel. The fossil fish there soon attracted his attention. The fossil-rich stones furnished by the slates of Glarus and the limestones of Monte Bolca were known at the time, but very little had been accomplished in the way of scientific study of them. Agassiz, as early as 1829, planned the publication of the work which, more than any other, laid the foundation of his worldwide fame. Five volumes of his Recherches sur les poissons fossiles ("Research on Fossil Fish") appeared at intervals from 1833 to 1843. They were magnificently illustrated, chiefly by Joseph Dinkel. In gathering materials for this work Agassiz visited the principal museums in Europe, and meeting Cuvier in Paris, he received much encouragement and assistance from him. They had known him for seven years at the time.