Paleoanthropologist Ella Al-Shamahi looks at the evidence for what people want in a partner and how it changes as they get older. Psychologist Julia Stern from the University of Bremen shares the results of a study which recruited people from a singles night in a Berlin club and followed them for 13 years. Novelist Adele Parks explains why writing about bad boys is so much fun, and on the Bridget Jones scale of bad boys think more Hugh Grant and less Colin Firth.