Emergence of life—how and where?—An update based on recent ideas

Panspermic origins notwithstanding, life, assuming that it started on Earth, may have taken root as soon as it became geologically permissible. There are multiple possibilities for early biogenesis from complex inorganic/organic geochemistry at diverse geological niches. Recent theoretical calculations have revived the possibility of Earth having a rather reduced early atmosphere, and had refueled arguments for a surface origin of life. Laboratory modeling of possible prebiotic RNA polymerization has seen interesting experimental advances, although a plausible replicator-like molecule has not yet been produced. The hydrothermal origin school of thought has also seen an interesting postulation for life’s early emergence and evolution—within contiguous, porous hydrothermal iron-sulfide (FeS) compartments, leading to a non-free living last universal common ancestor (LUCA). A confined LUCA evolving later into free-living archaebacteria and eubacteria could potentially reconcile some problems of molecular divergence between these two kingdoms. There are, however, many unresolved problems, and experimental evidence for such a scheme is lacking. Here, recent updates and refinements to the mainstay hypotheses for the emergence of life on Earth are reviewed and discussed.