Whence the demise and fall of the RNA World?

The RNA World is an early developmental stage in biology before the DNA World. If the first life on Earth began as a cellular RNA life-form which later transitioned to a ribonucleoprotein (RNP) organism, it did not stay that way for long. The last universal common ancestor (LUCA) of all contemporary DNA life seems to have existed already by the late Hadean eon (ca. 4.2 Gyr ago). Understanding what could have driven the evolution of the RNA/RNP World to the DNA World at this early time necessitates a biogeodynamic contextualization of the co-evolution of life and the Hadean Earth environment. Here we draw a connection between recent findings about LUCA and its habitat to make inferences about the earliest biological entities. We argue that environmental conditions on Hadean Earth motivated the transition to a DNA world. Selection pressures on minimalist autonomous RNA/RNP protocells with ribozyme-driven heterotrophic or nascent autotrophic metabolisms favored stability and fidelity. Our findings do not preclude RNA or RNP organisms at the time of the LUCA. Short description A swift demise of the RNA World underscores the hardiness of early life on Hadean Earth rather than its vulnerability to extinction.