Gustave Le Bon

Le Bon became interested in the emerging field of anthropology in the 1870s and travelled throughout Europe, Asia and North Africa. Influenced by Charles Darwin, Herbert Spencer and Ernst Haeckel, Le Bon supported biological determinism and a hierarchical view of the races and sexes; after extensive field research, he posited a correlation between cranial capacity and intelligence... - Wiki

In L'Évolution de la Matière (1905), Le Bon anticipated the mass–energy equivalence, and in a 1922 letter to Albert Einstein complained about his lack of recognition. Einstein responded and conceded that a mass–energy equivalence had been proposed before him, but only the theory of relativity had cogently proved it.