Szostak began his talk by posing a question to the audience: Is life common in the universe, or is Earth a rare exception? While the discovery of exoplanets leads many to believe life could be widespread, Szostak said that the complexity of cell formation makes that seem less probable. Central to Szostak's talk was the "RNA World" hypothesis - the idea that early life initially revolved around RNA molecules before the advent of complex cellular structures.
In 1991, De Duve proposed a hypothesis about the origin of life that did not require any deity: the thioester world, a compound containing carbon, oxygen, hydrogen, and sulfur. On that primordial planet, still devoid of life, thioesters would have provided the energy necessary for chemical elements to react and form more complex molecules, such as the first genetic material, RNA.
