Something unappeased, unappeasable
4 billion years before present: the surface of a newly formed planet around a medium-sized star is beginning to cool down. It’s a violent place, bombarded by meteorites and riven by volcanic eruptions, with an atmosphere full of toxic gases. But almost as soon as water begins to form pools and oceans on its surface, something extraordinary happens. A molecule, or perhaps a set of molecules, capable of replicating itself arises.
This was the dawn of evolution. Once the first self-replicating entities appeared, natural selection kicked in, favouring any offspring with variations that made them better at replicating themselves. Soon the first simple cells appeared. The rest is prehistory.Billions of years later, some of the descendants of those first cells evolved into organisms intelligent enough to wonder what their very earliest ancestor was like. What molecule started it all? (…)
When biologists first started to ponder how life arose, the question seemed baffling. In all organisms alive today, the hard work is done by proteins. Proteins can twist and fold into a wild diversity of shapes, so they can do just about anything, including acting as enzymes, substances that catalyse a huge range of chemical reactions. However, the information needed to make proteins is stored in DNA molecules. You can’t make new proteins without DNA, and you can’t make new DNA without proteins. So which came first, proteins or DNA?
artwork { Chris Ofili }
