Research Suggests that Life on Earth Arose from RNA-DNA Mix

According to Scripps Research chemists, diamidophosphate (DAP), which was plausibly present on Earth before life arose, could have chemically knitted together deoxynucleosides into strands of primordial DNA. The finding, published recently in Angewandte Chemie, is the latest in a series of discoveries pointing to the possibility that DNA and RNA arose together as products of similar chemical reactions, and that the first self-replicating molecules—the first life forms on Earth—were mixes of the two.

The discovery may also lead to new practical applications in chemistry and biology, but its main significance is that it addresses the age-old question of how life on Earth first arose. In particular, it paves the way for more extensive studies of how self-replicating DNA-RNA mixes could have evolved and spread on the primordial Earth and ultimately seeded the more mature biology of modern organisms. "This finding is an important step toward the development of a detailed chemical model of how the first life forms originated on Earth," says study senior author Ramanarayanan Krishnamurthy.

The finding also nudges the field of origin-of-life chemistry away from the hypothesis that has dominated it in recent decades: The "RNA World" hypothesis posits that the first replicators were RNA-based, and that DNA arose only later as a product of RNA life forms. Krishnamurthy and others have doubted the RNA World hypothesis in part because RNA molecules may simply have been too "sticky" to serve as the first self-replicators.