There's no law of physics that will prevent we clever humans - and our enhanced descendants - from eventually building technologies that can maintain and arrange every aspect of our bodies exactly as we'd like them to be. Technologies that can find every out of place molecule or damaged component and promptly fix it up. Aging will be a thing of the past in that era of molecular nanotechnology, whenever it comes to pass.
Systems that can identify, manage and place trillions of molecules accurately are not a pipe dream; after all, we are already surrounded by examples. You, for example, are just such a system, albeit somewhat slow at self-assembly to full size. There's nothing in the laws of physics that jumps out and says we can't do this. It's just a matter of time.
If you have the technology base to build a nanoforge to assemble a brick, then you also have the technology base capable of simultaneously assembling and controlling a hundred million medical nanorobots of arbitrary design and programming. Or an artifical lung better than the real thing, or replacements for immune cells that never get old or worn. You get the idea. A brick is just as complex as any portion of the human body if you have to build the thing molecule by molecule; more fault-tolerant, but just as complex.
Our cells are already very impressive examples of adaptive machinery. The machines our descendants will build with the knowledge gained from today's study of biology will be even more impressive yet. Cells, for all their intricacy, are far less efficient and organized than the laws of physics permit. One day, that inefficiency and disorganization will be eliminated by machinery intended to augment or replace our cells, and everyone will be the better for it.
If's good to look ahead up the ladder every now and again to remind yourself why you climb it. The future is golden, if we can sort out the issues on these bottom rungs to ensure we make it there. I notice that a presentation by Christine Peterson of the Foresight Institute transcribed at Future Current touches on some of what may come:
Another consequence of this in the long-term, and I think this will be true in your lifetime, is what would happen if we have atomic-scale control of our bodies. In the mid-term timeframe I was talking about nailing cancer. No more cancer cells, so that people do not die of cancer anymore. With this level of technology, you move on. What’s left? What kind of disease could a human being have that could not be addressed with this level of technology eventually? It’s hard to say.
I suppose a massive accident - you’re hit by a truck. That could be the end. But in terms of disease, where there is time, it’s not clear what kind of disease you could have that would not be treatable with this level of technology. Basically, you want to put the atoms of your body back in a healthy arrangement.
What about aging? Aging, as we know, is a very complex process. There are many things that are all going on at one time, but all of them are misarrangements of atoms. In principle, if you could figure out what a healthy pattern of atoms and molecules in the body is, you could then restore that pattern. The goal, of course, is that you not disrupt the structure of the brain, because that is where your memories and your personality are. I don’t mind if everything from [the neck] down is rebuilt - start from scratch, make it all perfect. But up here [the brain] we need to keep the patterns.
Ultimately, I think aging is addressable. When that happens is very hard to say.