He was educated at the High School in Edinburgh then studied Medicine at Edinburgh University. Having obtained his MD at Edinburgh in 1814, Grant gave up medical practice in favor of marine biology and the zoology of invertebrates, living on a legacy from his father. As a materialist and freethinker, and politically radical, he was open to ideas in biology that were considered subversive in the climate of opinion prevailing in Britain after the Napoleonic Wars. He cited Erasmus Darwin's Zoönomia in his doctoral dissertation, a work which introduced the idea of evolution in poetical form.