The comments are interesting. There is apparently a sizeable segment of reasonably intelligent people who are simply unable to wrap their minds around the notion of humans who live in a youthful, healthy state for hundreds or thousands of years.
They seem stuck on a broken mental record that if you live that long your arteries will harden, your eyes will fail, your body will be riddled with cancer, and you will be mentally and/or emotionally crushed by the loss and sadness of a life that long.
They just don’t get it. Nobody is going to live very long if issues like heart disease, cancer, and all the rest of the litany of maladies the human body is subject to are not permanently solved. The very essense of life extension would have to be the conquering of disease and physical degeneration for starters, and then to the defeat of aging itself.
As the article Glenn links indicates, there are some (very few, but some) humans who physically age at a rate four times slower than normal humans, which would posit a life span of at least 300 years. All of these people have other, major debilitating problems, but their very existence seems to indicate that significant physical life extension in humans might be possible.
There is also the question of whether we would even know if there were a few healthy folks out there who’ve been around for the past couple of hundred years. If I were one of them, I’d certainly keep my head down.
Anyway, this is not what Singularitarians are talking about. We’re talking about nano-techniques that continually keep you healthy, and fix any signs of aging/degeneration as they appear. Your body is just a collection of cells. Cells can be repaired or replaced. Every cell in your body is replaced over a period of a handful of years. The problem is that your DNA starts replacing healthy cells with aging cells.
Other organisms – including large ones like turtles and whales – live naturally for more than 200 years. Eventually – and starting fairly soon, I think – we’re going to enter a self-reinforcing “life cycle” that will permit those who wish to do so to “bootstrap” themselves into longer and longer lives.
I think we’ll probably reach this “longevity escape velocity” sometime within the next thirty years or so.
Anyway, if your objections revolve around a fear of a disease-ridden, physically degenerating but much-extended old age, don’t write letters. You just don’t get what I’m talking about here, and I don’t feel like arguing with you.
As for the sadness/depression nature of other objections, well, at close to my “natural” limit of three-score-and-ten, I’ve learned that time really does heal all such wounds. And we are talking about a lot of time here.