Based on the RNA world hypothesis, we outline a possible evolutionary route from infrabiological systems to early protocells. To assess the scientific merits of the different models of prebiotic evolution and to suggest directions for future research, we investigate the diversity-maintaining ability, evolutionary/ecological stability, and evolvability criteria of existing RNA world model systems for the origin of life. We conclude that neither of the studied systems satisfies all of the aforementioned criteria, although some of them are more convincing than the others. Furthermore, we found that the most conspicuous features of the proposed prebiotic evolutionary scenarios are their increasing spatial inhomogeneity along with increasing plasticity, evolvability, and functional diversity. All of these characteristics change abruptly with the emergence of the protocells
