The problem with studying the past is filling the gaps in history. It is a problem for historians as much as it is for molecular biologists. Professionals and theorists discover ancient artifacts from given periods but the the space in between to the next known artifact is left only to imaginational renderings. An example of this is the Archaeopteryx and how it led to the postulate of the evolution of birds.

Cast of the Berlin specimen of Archaeopteryx lithographica, from the collections of UCMP.
Original at Humboldt University, Berlin.

Recently, a team of scientists have bridged a conceptual gap. A brief background: it is believed that all life evolved from one common ancestor. This mother of a mother cell was something of a basic bacteria, and used RNA instead of the more complex double stranded molecule DNA, which we use now. That change from the molecule of life changing from single stranded RNA into DNA is what allowed a boom of complexity leading to the eukaryotic cell and eventually you and I. What the team from The Scripps Research Institute created was an enzyme that they dubbed ribozyme, which helps to make a complementary strand from a parent RNA strand. Now when we think about DNA replication, there are multiple enzymes that are involved in the process (Helicase, Ligase, Gyrase just to name a few). Ribozyme might not be the whole answer but it is certainly a start. Further research could reveal the mechanism of this transition. I can't help but think that the genetic sequence of this enzyme is incredibly valuable. Could it be preserved? But this answer only leads us to further questions. In a world of RNA organisms, how did this enzyme come to be? Did it make copies of itself? It follows the nature of a dog chasing it's own tail.

1. Jonathan T. Sczepanski & Gerald F. Joyce. A Cross-chiral RNA Polymerase Ribozyme. Nature, 2014 DOI: 10.1038/nature13900

http://www.sciencedaily.com/releases/2014/10/141029141216.htm