People like to think that they are the most successful form of life on Earth, the result of billions of years of evolution by natural selection, forever improving the individuals that it operates on. This is wrong. Evolution is not about improving anything; it’s about producing many offspring that carry copies of your genes forward into later generations. By this criterion, the most successful forms of life on Earth are the unicellular life-forms, micro-organisms which have been around for billions of years without ever having to change their basic form.