David Attenborough asks three key questions: how and why did Darwin come up with his theory of evolution? Why do we think he was right? And why is it more important now than ever before?

David starts his journey in Darwin's home at Down House in Kent, where Darwin worried and puzzled over the origins of life. He goes back to his roots in Leicestershire, where he hunted for fossils as a child and where another schoolboy unearthed a significant find in the 1950s, and he revisits Cambridge University, where both he and Darwin studied and where many years later the DNA double helix was discovered, providing the foundations for genetics.

At the end of his journey in the Natural History Museum in London, David concludes that Darwin's great insight revolutionised the way in which we see the world. We now understand why there are so many different species, and why they are distributed in the way they are.

But above all, Darwin has shown us that we are not set apart from the natural world, and do not have dominion over it. We are subject to its laws and processes, as are all other animals on earth to which, indeed, we are related.

First broadcast: Sunday 1 Feb 2009 on BBC One. The programme is being shown again on Thursday 29th March 2012 on BBC Four and is occasionaly shown on the Eden channel. For further broadcast details, and for links to watch on iPlayer where available, visit bbc.co.uk.

• This programme was part of the Darwin Season.