31 Essays on Infinite Lifespans   Aubrey de Grey generation of 150-year-olds (defined as those who reach 150 and are aged at most 30 years younger than the first 150-year- old) – a group who are almost certainly already alive and may well be middle-aged – will not die unless at their own hand. THE SECOND WORST THING THAT CAN HAPPEN Anti-aging  medicine  worthy  of  the  name  does  not  yet exist and seems certain not to exist for at least 15–20 years. By “worthy of the name” I mean interventions that can reli- ably restore someone exhibiting age-related dysfunction to the physiological and cognitive robustness that they enjoyed in early adulthood. This fact is apparently such grim reading for those unlikely to survive long enough to see a cure for aging, that society allows the term “anti-aging medicine” to be used for products that have no discernible efficacy in even slowing aging down, let alone reversing it. [4] Such people have an alternative to the certainty of permanent oblivion, however: oblivion that may well be permanent but may, just possibly, be only tem- porary.  Cryopreservation  is  catching  on,  slowly  but  surely: around 1000 individuals are signed up to have their heads (and sometimes also their bodies) immersed in liquid nitro- gen upon their clinical and legal death. [5] This may sound like very few, but not when we consider how resistant the general public remains to the idea of serious life extension by purely biomedical means (even as a goal, let alone a foreseeable one). [6] In fact, I surmise that cryonics sign-ups are a respect- able and probably increasing proportion of that small group who embrace the goal of extreme life extension – and this is hardly surprising, given the simplicity of arguments such as Merkle’s  characteristically  razor-sharp  quotation:  “Cryonics is an experiment. So far the control group isn’t doing very