Here is Chris’ answer to question 4, for me it was the most important because of its critical edge. Question 2 was about moderate or maximum life extension commitment and the question below is not restricted to maximum LE and unlimited lifespan but includes modest trials too.
4. What is the most probable technological draft of human life extension, which technology or discipline has the biggest chance to reach it earliest?(regenerative medicine, nanotechnology, gene therapy, caloric restriction, bionics, hormones, antioxidants, …)
In a hundred years, we won’t be able to look back and answer that question in a clear way. People who are committed to extending their lifespans will have taken multiple strategies. One can’t point to a life and say, these ten years were from exercise but these five were from resveratrol.
I think the first really useful technological life extension will have a very familiar form, e.g., “take this pill and call me in fifty years when you’re still alive.” Drugs that activate sirtuins and related pathways are very promising (I can’t spill the beans but I saw some amazing data at Cold Spring Harbor suggesting that there are already several working drugs). Once we’re better able to get our brains around calorie restriction, I think that CR mimetics will be right behind the sirtuin-based drugs. To the extent that these sorts of drugs will help prevent acknowledged illnesses like Type II diabetes, there’s already a clinical indication for them, so they should sail through approval on that basis.
As for the more exotic stuff: We’re close to therapeutic uses for stem cells, and within five to ten years we will be using stem cells to treat certain age-related diseases. I’m skeptical about using stem cells in broad, whole-body techniques; I don’t think we know enough about the aged tissue microenvironment to even know what to expect. Based on my own research (currently identifying the ways in which aged tissue stimulates the growth of cancers) and that of others (especially the idea that persistent adult stem cells are the ones that initiate many tumors), I’m not enthusiastic about the idea of putting a lot of telomerase-positive cells into old people and seeing what happens. We’re not there yet, knowledge-wise.
Gene therapy: Again, I think it will be useful soon in limited contexts, especially those in which we can remove cells from the body and then return them. The idea of very large-scale remodeling of genomes in many or most cells of the body is both frightening (we have nanoscale self-replicating genome-remodelers already; they’re called “viruses”) and hard (our entire immune systems would be up in arms against the attempt, and we’ve been trying very hard for a long time to solve that problem for transplants). Given the prior two points, major overhauls via gene therapy are outside the scope of our ability to meaningfully predict.
Finally: despite the hundred pounds of hype, bio-nanotechnology is really, really far away. Anyone who says otherwise either doesn’t understand nanotechnology or doesn’t understand biology, and is skipping a lot of important parts of the story. I’d put it firmly in last place.