Inspired by Darwin and Mendeleev, Aleksandr Ivanovich Oparin (1894–1980) was one of the first scientists to propose that the origin of life on earth was preceded by a period of nonbiological molecular evolution. Origin of Life, published in English in 1938 and still in print, "purports to show the gradual evolution of organic substances and the manner by which ever newer properties, subject to laws of a higher order, were superimposed step by step upon the erstwhile simple and elementary properties of matter." Written for a popular audience, Origin of Life remains a classic introduction to origin-of-life research.