Greatly influenced by the writings of Charles Darwin, including his book, The Origin of Species (Darwin, 1995; Richards, 2000), Lombroso derived his own proposals through scientific examination of Italian prisoners and army personnel. He advanced that criminals and delinquents could be distinguished by certain stigmata, including big lips and ears, flattened nose, skull shape, superior strength on the left side, and ability to withstand pain. Other propositions indicative of a predisposition to criminal behavior included a predilection for tattoos and orgies.