Early Earth Was a Molten, Asteroid-Blasted Hellscape. Scientists Now Know When That Changed

The question of life’s origins is a chicken-and-egg problem that is perhaps best explained by the ribosome. These tiny intercellular structures translate genes into proteins, a process essential to life. And yet, ribosomes themselves are made of proteins and RNA. So which came first, the ribosomes that make proteins, or the proteins that make ribosomes?

In the early 1960s, the RNA world hypothesis emerged as an answer to this question. RNA is the single-stranded cousin of DNA, the molecule that contains the genetic information for cellular biology. Often called the “workhorse molecule” of cells, RNA can take three different forms to serve three different functions. Messenger RNA (mRNA) carries genetic instructions from DNA to protein-making ribosomes, ribosomal RNA (rRNA) helps make the ribosomes themselves, and transfer RNA (tRNA) synthesizes proteins from mRNA.