Originally, ideas about Darwinian evolution at the level of individual molecules were experimentally demonstrated in References (1, 2) and theoretically conceptualized described in Reference (3) as below.
Surprised that such a respected journal and authors of the article omit citation of the fundamental prior art in the field.
1. Spiegelman S, Haruna I, Holland IB, Beaudreau G, Mills D. The synthesis of a self-propagating and infectious nucleic acid with a purified enzyme. Proc Natl Acad Sci U S A. 1965 Sep;54(3):919–927.
2. Mills DR, Peterson RL, Spiegelman S. An extracellular Darwinian experiment with a self-duplicating nucleic acid molecule. Proc Natl Acad Sci U S A. 1967 Jul;58(1):217–224.
3. Eigen, 1971; M. Eigen. Self-Organisation of Matter and the Evolution of Biological Macromolecules. Naturwissenschaften, 58 (1971), pp. 465–523.