Professor Robert Winston presents a documentary series that examines the armoury of instincts that help keep humans alive. For our ancient ancestors, beating the opposition was vitally important. It meant that they were more likely to survive and procreate. Those who got a kick out of winning were more successful and passed the desire for victory onto their children. So, over generations, our bodies have evolved to give us a feeling of euphoria when we win and a terrible feeling of despondency when we lose.