Ancient Yet Alive: Stable Molecular Networks and Precellular Polymer Consortia as Frameworks for Alternative Hereditary Systems Before LUCA

The origin of life is commonly framed within the RNA World hypothesis, yet increasing evidence suggests that early evolution may have involved a broader diversity of hereditary systems than those preserved in modern biology. Alternative informational polymers, compositional inheritance, autocatalytic networks, and compartmentalized molecular communities have all been proposed as mechanisms that may have preceded modern genome-based heredity. Building upon these concepts, we propose that the fundamental unit of early evolution may have been neither the gene nor the organism, but persistent molecular networks capable of maintaining organizational continuity through time. We define Stable Molecular Networks (SMNs) as interacting systems of informational polymers, catalytic oligomers, metabolites, compartments, and environmental feedback processes that maintain continuity despite continual molecular turnover. We further propose that compartmentalized SMNs could form molecular ecosystems termed Precellular Polymer Consortia (PPCs), in which heredity emerges from network organization rather than genome replication alone. Within PPCs, selective interactions, molecular memory, ecological feedback, and distributed information exchange may generate lineage-like evolutionary processes that we term precellular speciation. To connect these concepts to extant biology, we examine archaeal and bacterial systems that preserve organizational principles potentially relevant to early evolution, including CRISPR-Cas adaptive memory systems, ancient RNA-based molecular machines such as the ribosome and RNase P, hydrothermal vent archaea, chemolithotrophic microorganisms, syntrophic consortia, and complex microbial communities. Although these systems are not direct descendants of precellular networks, they provide experimentally accessible examples of molecular memory, distributed information processing, protometabolism, ecological cooperation, and system-level organization. Finally, we propose PLURIBUS (Planetary Liquid Universal Polymer Identification By Ultrasensitive Sequencing) as a framework for discovering noncanonical informational polymers, novel RNA modifications, and alternative hereditary systems within Earth’s microbial biosphere, particularly among poorly characterized archaeal and extremophile communities. Knowledge gained from these environments may ultimately support the development of more general life-detection strategies for planetary exploration. Together, these perspectives suggest that extant microbial ecosystems provide valuable experimental windows into evolutionary processes that may have preceded modern cells, genomes, and the Last Universal Common Ancestor (LUCA).