On Start the Week Tom Sutcliffe asks whether altruism is best explained through evolutionary science or moral philosophy. David Sloan Wilson argues for the former and believes altruism is part of group dynamics and social behaviour. William MacAskill may study the moral case for doing good, but is more interested in the practical impact than the heroic sacrifice. The Mexican campaigner Lydia Cacho knows what it means to make enormous personal sacrifices for the sake of others - her exposure of sexual and physical abuse has led to numerous threats on her life. While the composer Tansy Davies attempts to bring to the stage human beings in extremis as she creates an opera based on the events of 9/11.

Producer: Luke Mulhall.