If you want to break the world record for human longevity, the person you need to beat is Frenchwoman Jeanne Calment , who died in 1997 aged 122 years and 5 months. As her record has stood for 21 years, does it represent a limit for human lifespan, or will it be eclipsed?

Dislodging Calment is not an easy prospect. When you get really old – above 105 – your odds of making it from one birthday to the next are a little less than evens . How often have you tossed …