We'll probably never know exactly how life on Earth got its start. The conditions in which it began have long since been lost, and there are simply too many precursor molecules and potential environments that could have gotten the process going. Nevertheless, researchers hope to put together a pathway that's at least plausible, starting from simple molecules that were present on the early Earth and building up to an enclosed system with basic inheritance (from there, evolution can take over).
A lot of progress has been made in understanding how a simple chemical, like hydrogen cyanide, can be built up through a series of reactions into a nucleotide, the basic building block of molecules like DNA and RNA. And we've learned quite a bit about how larger RNAs (more than 100 nucleotides long) can fold into complex structures that can catalyze reactions and undergo the chemical equivalent of Darwinian evolution. The challenge has been bridging the gap between the two, going from a handful of linked nucleotides to a large molecule that's potentially capable of catalyzing chemical reactions.
Now, the team that developed the earlier results is back with another publication. Their latest work shows how short molecules that are composed of just a handful of nucleotides can be linked together, eventually building longer, more complex chains. Once again, the chemistry is simple enough to occur on the early Earth, and the reaction might explain a curious bias in how DNA and RNA are built into long chains of nucleotides.