Inspired by Richard Dawkins book 'The Ancestor's tale: a pilgrimage to the dawn of life' the 'Ancestor's Trail' is intended as a celebration of evolution. Darwin's Tree is represented by footpaths over the Quantock hills and whilst some walkers will begin the 13 mile hike representing the human journey others may join as elephants, reptiles or even jellyfish further down the line. Clare Balding meets those taking part in the celebrations and finds out why they feel evolution itself should be celebrated.