DNA, RNA and proteins are all molecules with a history. The study of how they have changed over time has given us a new perspective on evolution, and our place in nature. At the genetic level, evolution can be summed up as the production of new genes, their inheritance, and their selection by interactions with the environment. The fluid and dynamic nature of DNA has caused cellular life to fan out from the microbes that populated the Earth nearly four billion years ago, to the rich diversity of species we have today.

Origins

Creationists – who believe that God put each species on Earth fully formed – are conveniently sidestepping one of the toughest problems in science, that of how life began. Charles Darwin developed a convincing theory of how the earliest life forms evolved into more complex organisms. But he could not say how the first organism - often called the progenote – arose.

We will probably never know the truth about the origins of life, but there is no shortage of theories. Chemistry, cosmology and geology have all provided far more fruitful and imaginative notions about how life emerged on this planet than the creationists' stereotyped theories.

Before exploring some of the scientific ideas about the origins of life – and DNA – we ought to set the scene by trying to imagine just what our planet was like in its youth. This is not the place to go into complicated cosmological theories, so we will accept that the Universe came into being around 15 billion years ago with an event called the Big Bang.