I read Freeman Dyson’s short book “Origins of Life,” which presents his dual origin hypothesis on that subject. This early passage spells it out:
Either life began only once, with the functions of replication and metabolism already present in rudimentary form and linked together from the beginning, or life began twice, with two separate kinds of creatures, one capable of metabolism without exact replication and the other capable of replication without metabolism. If life began twice, the first beginning must have been with molecules resembling proteins, and the second beginning with molecules resembling nucleic acids. The first protein creatures might have existed independently for a long time, eating and growing and gradually evolving a more efficient metabolic apparatus. The nucleic acid creatures must have been obligatory parasites from the start, preying upon the protein creatures and using the products of protein metabolism to achieve their own replication.
Here is a video, maybe from 1998, of Dyson discussing it. A quotation towards the end:
By and large I would say that the experiments are still completely neutral. There’s no evidence one way ore the other whether replication came first or whether metabolism came first. The biologists all believe replication came first.
That’s the RNA world, which I haven’t studied. The link goes to a 1986 article by Gilbert.
I would like to learn more about the analogies Dyson makes in this passage:
To me, one of the most attractive features of the two-stage theory of the origin of life is that it shows life following the same pattern at three crucial periods of its history: first, the period of origins, when the two stages were metabolism and replication; second, the evolution of eucaryotic cells according to Margulis, when the two stages were parasitic invasion and symbiosis; and third, the evolution of higher organisms, when the two stages were the embryo and the package of cells that grew into an adult.