Aschwin de Wolf continues to republish important writing from the early days of the modern healthy life extension community at Depressed Metabolism. Those were the years of the late 1960s, in which the seeds were laid for the cryonics community on the one hand and pro-longevity supplement and "anti-aging" groups on the other. There's really a deep divide between the two factions in terms of fundamental philosophy: on the one hand aiming a few more years (or decades, as they overoptimistically thought at the time) of healthy life via applied pharmacology, on the other the engineer's path to defeating death completely. Quite different worlds of ambition - and as it turned out, rationality. The cryonicists, with visions of immortality in their sights, were far more correct about the bounds of the possible, given scientific knowledge at the time.

Once vitrified and stored at low temperature, a cryopreserved individual has time and the astounding curve of scientific progress on his side. The laws of physics and our present understanding of brain biochemistry place no obstacles in the path of restoring cryopreserved people - it's a matter of developing the necessary medical technology, and remaining well-stored until that time comes to pass.

Now "immortality" is a much abused term, cast widely and with many colloquial meanings. Linguistic drift has come to put it somewhere between "long-lived" and "ageless but vulnerable to accident" in all but more precisely spoken communities. But it was much used by the early cryonicists in a way closer to the dictionary definition, and that more than anything else I think captures their excitement at having envisioned the scientific doorway out of the trap - a tool that could provide a possible way around death. For example, the early cryonics book "Immortality: Physically, Scientifically, Now" by Ev Cooper, subtitled "A reasonable guarantee of bodily preservation, a general discussion, and research targets":

Though few, if any, cryonicists today can retrace their personal interest in cryonics to Ev Cooper, and despite the broader recognition of Robert Ettinger’s later-published work, “The Prospect of Immortality,” Ev Cooper’s privately published 1962 manuscript, “Immortality: Physically, Scientifically, Now,” represents the first major treatise on what would later become known as cryonics. Soon afterward Ev also started the first cryonics organization, the Life Extension Society (LES), from which several other cryonics societies eventually emerged. ... A handful of prophets: H. G. Wells, G. B. Shaw, Jules Verne, Capek, and Tsiolkovsky made some startlingly accurate predictions in the late 19th and early 20th centuries. The more sober members of mankind never held to them seriously, neither then nor now, passing them off as the successes amongst the law of chance. No matter how it came about - and some of these men were of acute scientific understanding and broad perspective - many of the possibilities they spoke of did come to pass: rocket travel, atomic energy, automatons that work in offices and run factories - too many to list. Now in the last half of the 20th century, to take seriously that physical immortality, here on earth, is scientifically possible is almost as much as dream can encompass, certainly more than sobriety can allow. This is perhaps a necessity, for it is only more absurd to chase after every South Sea bubble. And, ever since prehistoric man first imagined the possibility of life forever, the countless rolling centuries have not given him one shred of material verifiable evidence. Now, however, when some of the scientific possibilities appear on the horizon, someone has to form the question, consider a reversal of the skepticism engendered by centuries of disappointment and prepare the way for the reality of the incredible.

Why was cryonics envisaged as the step directly to immortality? Because, should the plausible outline of the process work, it is a gate to the future of far more capable technology. A future after the biotech revolution, in which our biochemistry does our bidding, aging can be repaired, and molecular manufacturing is in full swing. An age of bioartificial bodies, minds transferred to new and more robust mechanisms, strong artificial intelligences, and indeed, anything you might imagine that the laws of physics permit and enough time has passed to develop.

I'm not going to try to convince you that the future will be a golden, wondrous place: either you accept the implications of the present rate of progress towards what the laws of physics make possible, in which case you've probably thought this all through at some point, or you don't. Life, space travel, AI, the building blocks of matter: we'll have made large inroads into bending it all to our will within another half century. Many of us will live to see it even without the benefits of medical technology to come: growing up in a 1970s urban area will be the new 1900s farmboy youth come 2040; a strange and primitive near-past erased by progress, for all that so many people still alive actually lived it, time travellers in their own lifetimes.

In any case, I think it's interesting to ponder why cryonics is no longer seen quite so stridently as the gate to immortality, despite the fact that cryonics technology has advanced steadily since the 1960s, as has our understanding of our brain's biochemistry. Could it be because that the horizon for successful restoration has pulled in - perhaps as early as the 2040s? Cryonics advocates no longer expect to be restored to a time massively different to our own, because the journey will likely be one of decades rather than centuries.

The vision of immortality can still be conjured just as stridently, should we so wish, but it's somewhat fashionable at the moment to distance oneself from talking about immortality. There are practical aspects too. Now that we have serious, scientific work taking place aimed at the repair of aging, and fundraising for faster progress is an earnest endeavor, one can't afford to be throwing around words that can be easily misconstrued. The path to moderation of the vision is hard to avoid once money starts flowing in.

I started on the path that led to the Longevity Meme and Fight Aging! from the position that immortality was a good thing, and knowing that the laws of physics did not disallow a damn good attempt at actual immortality - the "no death, ever" dictionary definition - or at least a life span of millions of years on the way to that end goal. If that's not long enough to figure out the aspects of the problem that cannot be answered today, I'm not sure what would be. If I'd been born two decades earlier, I'd have been a cryonics advocate and volunteer. As it is, it looks like these first decades of the 21st century are the era in which step one (of thousands, no doubt) of simply remaining alive forever - continuously repairing aging in these bodies of ours - can be achieved.

A philosophy of first things first is a good way to temper visions of steps two through however many thousand, and explains why I spend my time talking about the Strategies for Engineered Negligible Senescence and the biotechnology revolution. If we don't complete the first step, sufficient control over our biochemistry to repair aging, then it's all for nothing.

So, the million year life span: how could that be achieved? The short, and not terribly informative answer is that you get it done by using advancing technology to dramatically reduce your vulnerability to fatal accidents, murder, and the like. If you project out the accident rates for life today, you'll see that an ageless human, sustained by forseeable biotechnologies of cellular and biochemical repair, has a life expectancy in the 1000 to 5000 year range. Sooner or later that piano is going to fall on you hard enough that even advanced medical technology can't fix you up.

Once you start looking at living for 100,000 years in much the same shape as you are today, it becomes apparent that almost any activity bears a level of risk that'll jump up and kill you. Eating, swimming, reading ... breathing. Stretch out the time for long enough and the improbable and fatal will happen to you.

The answer is to change the shape you are. Getting past step one, the repair of aging, gives you a few hundred years of comparative statistical safety. I can't imagine that much of the technology needed for step two will remain beyond the human civilization of the 2200s. Your step two will no doubt vary, but I would get my neurons replaced (slowly, one at a time over time, to ensure continuity of the self) with some form of much more robust, easily maintained nanomachinery. That allows these sorts of engineering possibilities:

Swapping out the body for whatever machinery of transport and support best minimizes risk

Moving most of the business of life into simulation

Physically separating my neurons while still remaining alive, conscious and active

It's that last point that's key, as physical locations have the same sort of issues with time, probability and bad events as people do. Meteorites happen, as do landslides, earthquakes and volcanoes. The way to reduce your risk function dramatically is to spread out. You can imagine a wireless brain (using whatever the most robust communications technology of the time happens to be be) scattered in a thousand separate locations across a continent, or the whole planet.

That should be good for 10,000 years of falling pianos of various types. However, once you start digging back into the geological and astrophysical history of the solar system, it's clear that spreading out over an entire planet still leaves you at risk on longer timescales. Probably not from impacts: I'll be surprised if we can't solve that problem within few centuries from now. There's always war, nearby supernovae, massive unexpected solar flares, and other unpleasant items, however. The supernovae are the biggest of the known concerns, given that I expect it'll be a long, long time before preventing them is a practical and ongoing business for the civilizations that follow man.

Spreading out is an option again: boost up the size of your components and neuromachinery for worst-case-scenario radiation projections, provide them with the means to move about the solar system, and become a spacefaring entity, spread out over a sizeable selection of orbits. By that point in time, your physical presence resembles a small country of nanomachinery, automation and delegation. The trade-off for spreading out and further greatly reducing your long-term risk of death is that you slow down. The speed of thought is determined by the speed of communication between neurons in components in different orbits. If your brain is light hours wide, you will live very slowly indeed - but for so long, that you come out ahead.

There are other paths forward, of course, with varying degrees of risk and invention. I haven't touched living very fast in simulation by running your brain on faster hardware, for example. The practicality and possibilities as determined by the laws of physics and what we have invented to date have been debated well over the past decades of the transhumanist community; if you head out there online to look, you'll find a wealth of fascinating material.

Is immortality impractical? Given the risk functions and uncertainty in the timeline for completing the repair of aging, it might be unlikely for most of us alive today because we won't get past step one. But it's far too early to say whether immortality, the "no death, ever" version, is actually impossible for all of us. Give it a million years and ask me again. The slope of technology and possibility is curving up ahead of us to great heights, and it'll be a wild ride either way.