While many dinosaurs were wiped out when a colossal asteroid struck Earth 66m years ago, one group survived: birds. Prof Steve Brusatte, a palaeontologist at the University of Edinburgh, has written a new book, The Story of Birds, tracing the evolution of our feathered friends from their dinosaur origins. He joins science correspondent Nicola Davis to discuss how scales first became feathers, how winged dinosaurs survived the impact of the asteroid and why their extreme adaptability offers hope that birds might also make it through the current environmental crisis