The first time a fish crawled out of the water and onto land, it was a turning point that led to brand new kinds of life. But this couldn’t happen on its own: that fish would have needed both lungs and legs.

Neil Shubin, evolutionary biologist and author of Some Assembly Required (£18.99, Oneworld), says that fish didn’t evolve these traits to help them live on land. In fact, the reason they could live on land was that they repurposed the body parts they had already.

The same remarkable changes have happened all through evolutionary history, from the first vertebrate life to the first flying dinosaurs.

He speaks to our Online assistant Sara Rigby.

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