Transcript

Sir Paul Nurse: The third idea I want to talk about is evolution by natural selection. So where did this come about? Well, it came about because of this Victorian gentlemen here, Charles Darwin. Now Darwin had two ideas: that evolution took place, and that it took place by natural selection.
The first of those ideas was not his. It actually has its origins with the ancient Greeks who talk a little bit about evolution. Early church fathers like Augustine argued a lot about evolution. And most interestingly for this talk, Charles’ grandfather, Erasmus Darwin, 70 years before was a great advocate of evolution. Charles then did not invent the idea of evolution. What he did do was marshal together a huge amount of data, particularly on fossils, to indicate that he thought evolution had taken place.

Secondly, and most importantly ,he proposed the idea of natural selection - evolution by natural selection. So he provided a mechanism, a very powerful mechanism, for how life could actually evolve. And to think about that, I’m going to define the properties of life that are needed for natural selection to take place. There are three. The first is that life must reproduce. Secondly, life has a hereditary system whereby information defining how that living organism works is copied or inherited during the reproductive process. Thirdly, that hereditary system must exhibit some variability. And it's that variability upon which natural selection can work - because the clever idea about natural selection is that those organisms which are most successful because they have genetic variations that make them successful, will breed better and provide more offspring to the next generation. So the population, the next generation's population, is more likely to have those favourable varieties represented at a higher level. So gradually the composition of the population will change. That leads to evolutionary change, and eventually to the formation of species.