66 million years ago, a huge asteroid hit the earth, wiping out most of the dinosaurs that roamed the land. It would still be tens of millions of years before the first humans appeared – but what if those dinosaurs hadn’t died out? Would we ever have evolved? Dive back into the past to see how our distant mammal ancestors managed to live alongside huge, fierce dinosaurs; and why the disappearance of those dinosaurs was great news for mammals. This episode of CrowdScience is presented by Marnie Chesterton and Anand Jagatia for the BBC World Service.