What Is the RNA World Hypothesis?

Evolution probably goes back before cells. The first living thing would have to be a self-replicating molecule that uses energy. Different forms of this self-replicating molecule would have different reproductive success. There is a not-unpopular theory that the original form of life on earth was an RNA molecule. RNA is a special molecule, because it can both act as a store of data, and as an enzyme for catalyzing reactions. According to this theory, specialized data storage in the form of DNA evolved later, along with specialized enzymes. Here's a brief overview of the theory that shows how evolution could happen with chains of RNA only: [this video] Jack Szostak at Harvard has a great series of videos explaining this theory, and also a number of experiments that he and his students have performed. [link]