3.1 Evolution and natural selection

What was the crux of Darwin's ideas?

Darwin described his own theory in a pretty tight nutshell. Evolution, he said, is descent with modification. Descent – the passage of information, we would say, today, from one generation to the next and modification – the fact that that passage is imperfect. Over time, those changes will build up and you will get change. It's inevitable. It's bound to happen. But we can rephrase that in slightly more telling terms today. We can say, evolution is genetics plus time. If you've got genetics, DNA, all that stuff – if it copies itself with mistakes, that's mutations. And if you've got time – and we got three and a half thousand million years since the origin of life– evolution is absolutely inevitable. So that's the core of Darwin's theory. It's extraordinarily simple. But Darwin had a second idea, and that's really where he was so smart, because he realised that what's being copied in biology is itself a copying machine, so that if one version inherits a change, a mutation, which makes it more likely that it will survive and reproduce itself, then that change will become more common and will spread. And over time, those differences will build up and new forms of life will emerge by what he called natural selection – inherited differences in the chances of reproducing. So that's Darwinism in one minute.