The debate over the degree to which aging is programmed into our biochemistry still continues. An example from ScienceDaily: " To date, there are two basic concepts of reasons for ageing. The first one is death as a result of damage accumulation, and the second is death as a suicide program. There are multiple arguments in favour of both concepts. A new - astrocytic - hypothesis has been put forward ... In the framework of this hypothesis, ageing is treated as a result of changes in cerebrum cells. The key role is played by transmutation of cells of the radial neuroglia into stellate cells - astrocytes. Since such cell transmutation is a programmed process, the researcher is inclined to the opinion that ageing and following death have been programmed." The SENS approach, treating all change as damage and working to fix it, somewhat sidesteps this debate. It doesn't matter why change happens with age: just figure out what it looks like at the biochemical and cellular level, and then develop a fix for it. Engineering, especially medical engineering, is all about working around the unknowns to attain a good result.