Why longevity? For a number of years, the Fondation IPSEN has been devoting considerable effort to the various aspects of ageing, not only to age-related diseases such as Alzheimer's, but also to the Centenarians, the paragon of positive ageing. The logical continuation of this approach is to address the question of longevity in global terms. Behind the extreme values, what span is accessible to all of us and likely to directly concern most of our contemporaries? The individual and col lective increase in the duration of life is one of the most striking phenomena of our time. It could be one...