What makes us good or evil? It's a simple but deeply unsettling question. One that scientists are now starting to answer. Horizon meets the researchers who have studied some of the most terrifying people behind bars - psychopathic killers. But there was a shock in store for one of these scientists, Professor Jim Fallon, when he discovered that he had the profile of a psychopath. And the reason he didn't turn out to be a killer holds important lessons for all of us. We meet the scientist who believes he has found the moral molecule and the man who is using this new understanding to rewrite our ideas of crime and punishment.
Kate Humble journeys to the far north of Siberia in the teeth of the Arctic winter to travel with the Nenets. These reindeer herders spend their lives migrating with the seasons up and down the Yamal Peninsula, following their herds from pasture to pasture. But it's a tough and precarious existence, living in temperatures that can drop to -54C. And the extremes soon take a toll on Kate - a lover of warm weather - and her crew, when on the way to meet their Nenets family their vehicle breaks down and they're forced to abandon their plans.
Population statistics are like crystal balls -- when examined closely, they can help predict a country's future (and give important clues about the past). Kim Preshoff explains how using a visual tool called a population pyramid helps policymakers and social scientists make sense of the statistics, using three different countries' pyramids as examples.