How long is a life?

Not long ago I was asked (being a doctor) to appear in a public discussion on the subject of longevity. My ignorance of the subject seemed to the organiser a novel—and indeed a not quite sufficient or respectable—reason for refusal.

One of the proposed panellists was an eminent scientist who believed that we were on the verge of abolishing death; which abolition, were it ever to be brought about, would be grossly unfair to all those people who had died in the previous centuries.

However, I suspected (without having an evidence base for my suspicion) that the scientist was talking nonsense. Of course, the natural span of human life has long been a matter of speculation. For example, …