Up until 10-40,000 years ago, the whole world looked as the safari parks of east Africa do today. North America would have been teeming with lions and mammoths, the Amazon and Australia would have had giant creatures, and Europe would have been home to elephants, hippos and rhinos. What has the impact of the loss of megafauna been, and should we seek to bring it back through 'rewilding'? A conference in Oxford from 18-20 March will investigate these questions.