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Jan Zalasiewicz, Professor of Palaeobiology at Leicester University, talks to Jim al-Khalili about the Anthropocene, the concept that humans now drive much geology on the earth. He's one of the leading lights in the community of scientists who are working to get the Anthropocene, the Age of Man, recognised.

They discuss the controversy about the date of when it began- some say it was a thousand years ago, or the Industrial revolution, others that it was the Second World War, and yet others that it's as recent as the 1960s. It all turns on finding the Golden Spike, a layer in rock strata above which the geology changes.

Jan Zalasiewicz began his career as a traditional geologist studying rocks 500 million years old in Welsh border. After years out in the field mapping the landscape for the British Geological Survey he moved into academia at Leicester University.