Geologists like to divide up history into epochs, or eras, separated by events that leave an indelible mark in the geological record of the earth - for example, the meteorite strike that finished off the dinosaurs 66 million years ago, whose impact is written in rocks across the globe. Similarly we humans have made our own irreversible impact on the planet, ushering in what's become known as the anthropocene era. But when did it actually start? Simon Lewis spoke to Kat Arney about how he's has been figuring it out. Like this podcast? Please help us by supporting the Naked Scientists