Melvyn Bragg and guests Martin Brasier, Richard Corfield and Rachel Wood discuss the Ediacara Biota, the Precambrian life forms which vanished 542 million years ago, and whose discovery proved Darwin right in a way he never imagined. Darwin was convinced that there must have been life before the Cambrian era, but he didn't think it was possible for fossils like the Ediacara to have been preserved. These sea-bed organisms were first unearthed in the 19th century, but were only recognised as Precambrian in the mid-20th century. This was an astonishing discovery. Ever since, scientists have been working to determine its significance. Were the Ediacara the earliest forms of animal life? Or were they a Darwinian dead end? Either way, it is argued, they reveal some of the secrets of the workings of evolution. Richard Corfield is Senior Lecturer in Earth Sciences at the Open University; Martin Brasier is Professor of Palaeobiology at the University of Oxford; Rachel Wood is Lecturer in Carbonate Geoscience at the University of Edinburgh.