A ball is a simple, everyday object that holds such a deep appeal for us. We have been playing with them since the dawn of time on every continent. Mike Williams finds out why. Some scientists argue that ball playing helped us become human, by developing the parts of the brain involved in speech, emotions and decision making. But why is ball playing fun? One explanation is that the unpredictability of never quite knowing where a ball will fall gives us the kinds of emotional highs and lows that would take unusually good fortune, or tragedy, to get otherwise. (Image: a young boy holding a ball. Credit: AFP/Getty Images)