The oldest well-documented human lived to the age of 122, but is there an upper limit to the human lifespan? Or could medical advances extend it indefinitely? By studying demographic literature in detail, Xiao Dong of the Albert Einstein College of Medicine in New York and colleagues have found strong evidence that there is indeed an upper limit determined by our biology, perhaps a byproduct of our fixed genetic programmes for early life events. Despite advances in medicine, the age at death of the oldest person has not increased since the 1990s.