In the age of Darwin, as man struggled to come to terms with his evolutionary history, life’s marine origins began to haunt the nineteenth-century imagination of the sea. Using Jules Michelet’s natural history of the ocean, The Sea (La Mer), I propose that evolutionary theory provoked a shift away from the Romantic poet’s easy identification with barren seascapes towards an evolutionary ocean filled with primitive life that deeply troubled modern man. Although Michelet traces human evolution within the marine, he struggles to identify with the sea’s violent, grotesque, and metamorphic biodiversity. Punning on the French word for mother (mer-mère), Michelet describes seawater as a mixture of reproductive fluids, detritus, and microscopic organisms that allows him to imagine the ocean as a global organism: birthing, copulating with, and consuming its own creations. In spite of its overwhelming fertility, the ocean evinces for Michelet a melancholy evolution, wherein history collects in the depths and paralyzes nature’s attempts to transcend its primitive past. Analyzing Michelet’s representation of sea water, polyps, the whale, and the siren, I show how the emergence of a gendered, melancholy imagination of the evolutionary ocean fundamentally changed modernity’s relationships to the submarine.