Rafinesque’s family moved to France the year following his birth, and at age nineteen Rafinesque became an apprentice in the mercantile house of the Clifford Brothers in Philadelphia. He returned to Europe in 1805 and spent the next decade in Sicily, where he was secretary to the U. S. consul. During this time his first scientific books were published. He returned to the United States in 1815 and remained in America the rest of his life, becoming a naturalized citizen in 1832. He was professor of botany and natural science at Transylvania University in Lexington, Kentucky from 1819 to 1826.
The early conclusion by Rafinesque that the taxonomic categories called species and genera are man-made generalizations which have no physical existence led to his deep appreciation of variation in plants. He understood that such variation, through time, will lead to the development of what we call new species. But he had no explanation for the cause of variation, though he did consider hybridity a possible mechanism and, without calling it that, he had what appears to be some perception of mutation. Hence, he never developed a theory of evolution earlier than Darwin, as sometimes has been claimed, because Rafinesque had no inkling of natural selection and his understanding of geological time was far too shallow.