Why the expansion of the paleolithic brain was powered by cooked carbohydrates. Gareth Mitchell talks to Professor of Evolutionary Genetics, Mark Thomas, about the difficulties of establishing what our ancestors ate. More than half the world's corals grow in deep, cold waters, many around the shores of the British Isles. But a new study shows they are under severe threat from ocean acidification caused by increased levels of carbon dioxide. Gareth talks to Professor of Marine Biology, Murray Roberts, from Heriot Watt University about why these corals could all be gone by the end of the 21st century. This week's short-listed Royal Society Winton Prize book is Life's Greatest Secret: The Race to Crack the Genetic Code. Marnie Chesterton talks to the author Matthew Cobb. BBC Science and environment reporter, Jonathan Webb, joins Gareth from the American Chemical Society meeting in Boston to talk about why the grime on buildings could be a new source of air pollution and why carbon dioxide in the atmosphere could be used to make carbon fibres.