[guylhem]

Mortality is the #1 bug of human hardware (with cancer a close #2). It may have been a feature a few thousand years ago, with limited resources, but it's now hampering our progress.

I don't want mankind achievements to be limited by our limited lifespan. The first 20 to 30 years are wasted on learning - almost like 1/3 of a average life. But with linespans in the 200 to 300 years, that would be 10% - and these added productive years could bring so many more good things. Imagine if Feynman and Einstein were still alive today, having new ideas, discovering new things. Imagine if we still learn during 1/3 of the lifespan - the amount of knowledge that would be acquired, and the marvels we could achieve with it.

For those who will lament on how this would be bad/capitalism/not respecting nature or (insert your favorite deity), nobody will force you do to anything. Die of old age at 90 if you want.

Personally, I want extended life or immortality to do crazy thing when I'm still young in my early 200 (or young again thanks to cures we can't even imagine at the moment)

[Brakenshire]

I agree in the long run.

But you don't have to get very old before it's obvious that a lot of ageing is an accumulation of small infirmities that build up over time. There may well be a switch that can turn on or off the dramatic downturn that occurs in old age (perhaps to do with telomeres, or lossy DNA replication, or whatever), but it seems unlikely the same switch will also reverse that accumulation of infirmities. Returning a 60 year old body to the same maintenance processes as a 20 year old body won't fix torn cartilage, sciatica, or cardiovascular damage. So obviously we should be investigating the former processes, but the techniques for the latter small problems must be substantially fixed beforehand, or else we'll end up in this nightmarish middle zone of people getting more and more unwell, but not dying.

[ENGNR]

My limited understanding is that the repair processes also play a big part. For example bones become brittle because stem cells no longer fill the gaps as quickly as they appear. The body also fully replaces every cell every seven years. If they could find a way to just restore the repair mechanisms a whole host of problems could slowly start to disappear.

[reasonattlm]

Bones also suffer from other processes that damage the structural properties of the extracellular matrix such as cross-linking by hard to break down sugar compounds. There is also a process of growing cellular dysregulation wherein the ongoing bone remodeling favors destruction over construction, and that is distinct from stem cell decline. Every tissue is impacted by multiple forms of damage beyond loss of maintenance via stem cell function, some of which, like the cross-linking, accumulate slowly and cannot be repaired by our biochemistry. Clearance of some sort will be needed.

The body does not replace all of its cells; different tissues have different turnover rates. Many of the cells in your central nervous system will be with you for your entire life. There is research to suggest that even some of the individual proteins in those cells are never replaced either.

[Houshalter]

All we need to worry about is the brain. We could just grow headless clones and do brain transplants to fix everything else.

And soon after that we will be able to replace the brain too. Whether uploading to a computer, or adding so many artificial neurons, only a small part of you is still biological.

[pron]

But there will surely be other Feynmans and Einsteins. What difference does it make if that's the same person? Also, why do you assume that we'll acquire more knowledge than we already have? It makes sense to think (as the human brain is a huge energy sink), that our brains are just large enough to process information for one human lifetime. I don't remember most of what I learned at university, and that wasn't even two decades ago.

[manmal]

My only concern is overpopulation. What about that?

[photonic28]

If longevity becomes so prolific that overpopulation becomes a credible concern, then the right of the living will supercede the right of nonexistant future people. It makes a lot more sense to ration birthrates than it does to ask someone to die so that they may make room.

[forloop]

Intuitively it seems to be an issue. The mathematics, however, say not! The trouble with mathematics being correct is it doesn't convince most people, imo. Really it needs someone who people trust to tell them life extension is OK. Possibly a film star. Anyway, since we're on HN, here's a paper.

'Demographic Consequences of Defeating Aging'[0].

'A common objection against starting a large-scale biomedical war on aging is the fear of catastrophic population consequences (overpopulation). This fear is only exacerbated by the fact that no detailed demographic projections for radical life extension scenario have been conducted so far. This study explores different demographic scenarios and population projections, in order to clarify what could be the demographic consequences of a successful biomedical war on aging. A general conclusion of this study is that population changes are surprisingly slow in their response to a dramatic life extension. For example, we applied the cohort-component method of population projections to 2005 Swedish population for several scenarios of life extension and a fertility schedule observed in 2005. Even for very long 100-year projection horizon, with the most radical life extension scenario (assuming no aging at all after age 60), the total population increases by 22% only (from 9.1 to 11.0 million). Moreover, if some members of society reject to use new anti-aging technologies for some religious or any other reasons (inconvenience, non-compliance, fear of side effects, costs, etc.), then the total population size may even decrease over time. Thus, even in the case of the most radical life extension scenario, population growth could be relatively slow and may not necessarily lead to overpopulation. Therefore, the real concerns should be placed not on the threat of catastrophic population consequences (overpopulation), but rather on such potential obstacles to a success of biomedical war on aging, as scientific, organizational, and financial limitations.'

[0] http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3192186/

[pron]

As that paper very first assumption is both unlikely and shows a complete lack of imagination, I think its results are dubious. In addition, I seriously doubt that we hae the math to be able to predict this.

Here is what the paper says:

Let us start with the worst-case scenario (for overpopulation)—physical immortality... Consider a situation, when parents produce less than 2 children on average, so that each next generation is smaller than the previous one... This conclusion does not require any complex calculations and questionable assumptions, but follows directly from the calculus, and the property of infinite geometric series to converge

Well, I beg to differ with the "questionable assumption" part. Why would anyone think that in infinite time, parents will have, on average, less than two children?

And here's the lack of imagination: the whole (cultural) concept of "parents" and family dissolves when there's no death. If you marry at 1000, and stay married to your wife for 5000 years (producing one child), chances are that by the time you're 50000 you've likely forgotten your wife's name, and your only child's too. In fact, you won't even remember that happened (well, maybe you'll remember your first time around, but by your 200th marriage, you won't remember how many children you had with your 37th wife).

Of course, I may be suffering from lack of imagination, and the structure of society will be completely different. The point is that making any assumption on human behavior after such a revolution of much of what makes us human, is preposterous. Immortal humans will behave in ways that we cannot predict, and we therefore cannot predict how the population will grow.

[forloop]

From the paper: 'Even for very long 100-year projection horizon, with the most radical life extension scenario (assuming no aging at all after age 60), the total population increases by 22% only (from 9.1 to 11.0 million).'

That stat is for Sweden—in case anyone wonders where the numbers are from.

Anyway, that's for the next 100 years. In 5000 years one would hope the human race will be multi-planetary. Looking at the time-scale, concern is still misplaced.

[pron]

That number only makes sense of people are unable to reproduce as they age. There is probably no correlation between population growth of mortal humans and immortal humans. They may have 100x more children, and they may have almost none. You can't extrapolate after such a bifurcation in the model.

In 5000 years the human race might be multi-planetary, or extinct. We have absolutely no information to make such predictions or even estimate their likelihood.

[forloop]

Yes. In 5000 or 50000 years there may be a problem with overpopulation—or not.

When someone expresses concern for overpopulation due to life extension, what time span are they referring to? 50000 years? Probably not. Looking at population growth for 100 years as per the model, the conclusion of the paper holds:

> Therefore, the real concerns should be placed not on the threat of catastrophic population consequences (overpopulation), but rather on such potential obstacles to the success of a biomedical war on aging, such as scientific, organizational, and financial limitations.