Melvyn Bragg and guests discuss what happens when parents from different species have offspring, despite their genetic differences. In some cases, such as the zebra/donkey hybrid in the image above, the offspring are usually infertile but in others the genetic change can lead to new species with evolutionary advantages. Hybrids can occur naturally, yet most arise from human manipulation and Darwin's study of plant and animal domestication informed his ideas on natural selection. With Sandra Knapp Tropical Botanist at the Natural History Museum Nicola Nadeau Lecturer in Evolutionary Biology at the University of Sheffield And Steve Jones Senior Research Fellow in Genetics at University College London Producer: Simon Tillotson