not only the whole genome thing which i have read a tiny bit about...
but neurons. as age progresses naturally the synapses fire less and less, with weaker intensity. we can not figure out how to fix this now by "hand" so to say, how are we going to program tiny things to do something we don't even know how to do?
there's too many things it will take us millenium to figure out fully, and without the basic knowledge of how it works how will be able to explain it, or do it ourselves?
never will happen.