From David Holdsworth
You report the discovery of two exoplanets orbiting in the Goldilocks zone of Kepler 62, and speculate on the evolution of life there, even the possibility of it having evolved on each planet (27 April, p 10).
Although I believe that we should continue to look for extra-terrestrial life, I do not expect that we shall find it. While life is abundant on Earth, current theory has it that it is descended from a single ancestor cell. Yet Earth abounds with suitable habitats, so the conclusion must be that the initial emergence of life is highly improbable, and has happened just once in over 3 billion years on a highly suitable planet.
Settle, North Yorkshire, UK
