Rather than simply raising questions, I guess I should add some more to the discussion:
[NOTE: *please* do not quote this rough-draft passage off-list without explicit permission]
The HU-GOO catastrophe?
Here's the worst and most ironic question of all: would a true immortality treatment, emerging as a spin-off of the HUGO Project, telomerase investigations, or some other deep life sciences research effort, unleash the world's worst plague - an unstoppable tidal wave of endlessly reproducing human beings? It is all very well to mouth wishful platitudes about human intelligence and foresight, but those great gifts have let us down in the past, at least some of the time (although we're still here, despite owning nuclear and bacteriological weapons of mass destruction for over half a century). At other times, coupled to devotion, courage, honour and love, intelligence and foresight have been our salvation and our glory. Tangled through every fibre of human choice, however, is our deep-grained inheritance as the children of four billion years of driven replicators.
Any one of us can overcome, at least for a time, those inarticulate urgings and imperatives coded into our bodies by survivor genes. Any of us is able to delay parenthood for years or decades past the dizzying adolescence when Homo sapiens reproductive programs kick in with their wild hormonal songs, their heartbreaking melodies of loneliness and yearning. Any of us, given sufficient motivation, can choose a life path without any kind of parenting, or indeed any sexual expression at all - there are many voluntarily childless heterosexual people, gays, celibates, paraphiliacs with interesting tastes that preclude reproduction. But not all of us can deny those urging all the time - and it will be impossibly harder, perhaps, when we literally have all of time.
China has managed for two decades to restrict most couples to bearing only one child, within marriage, using an authoritarian and quite brutally invasive policing mechanism. Still, many Chinese citizens break the rules and have more than the one authorised `little emperor'. (Many of the little empresses die young, notoriously, which does show in a gruesome way that people can deny one of the most powerful instinctual drive even as they pursue the satisfactions of a related cultural pressure.) So what will happen if people learn to live for centuries or millennia, retaining all the fertility and juice of healthy young adulthood?
Here's the worst and most ironic answer of all.
The world would be swollen with hungry human mouths very quickly, by evolutionary measures, even if women only had a new baby or two every 20 or even 50 years. The most prodigious and Promethean technologies might find it impossible to meet our collective appetite for energy, raw materials, living space. Nanotechnology will make the driest deserts bloom, honeycomb the mountains, fill the oceans with self-sufficient artificial cities and the skies with geodesic homelands kilometres in diameter - but sooner or later, even with cheap transport off the planet and into the asteroids, a planet's worth of always-fertile immortals will choke Gaia's life-support systems, or go haywire into lethal carnage.
So, at least, it might seem. Malthus, who long ago forecast overpopulation doom, would prove to be the bleak prophet of utopia.
The new population bomb
Dr George D. Moffett's authoritative Critical Masses notes that in the mid-1990s world population was some 5.6 thousand million, and expected to double by 2035. (By July 1998, according to the US Bureau of Census, the global figure was estimated at 5,927,383,121.) In fecund Africa, doubling times are half the global average, and numbers would swell from 670 million to 1.4 billion by 2015. At some point, it was hoped, the most struggling nations would attain sufficient economic prosperity that women would move into `replacement fertility', stopping at no more than the two surviving children needed to replace her and their father(s). Yet population momentum would slow the impact of that transition. Two out of five humans in the poorest countries are under 15, readying themselves to add to that huge bulge. Strikingly, while Japan reached replacement fertility as long ago as 1957, its population would take half a century to become stationary (zero population growth) in the early 2000s.
And the world as a whole is nowhere near replacement fertility: the current level is four surviving children for every couple. Not even the appalling epidemic of AIDs will scythe that swelling human harvest. `Even with the projected losses,' Moffett notes of the plague, `population growth rates will remain high and population doubling times will be increased by only a few years.' On the other hand, if heterosexual people most at risk of AIDs in the Third World adopt condoms as a protective measure, that might in turn reduce runaway overpopulation.
So what happens if science extends life span significantly? Even `replacement fertility' would be excessive for a groaning planet, since those ageing adults whom the new babies were meant to replace will still be alive and kicking, consuming, polluting with their energy demands, and perhaps making even more babies. Prophets of population doom like Paul and Anne Ehrlich might be proved right after all.
The population prosperity engine
Is it true, though, that the new demographic transition into extended or rejuvenated life would have such terrible consequences? Optimists such as the late Julian Simon, a professor of business administration, argued vehemently that economic growth in human societies booms alongside population increase, without leading inevitably to resource depletion and environmental degradation. How so? Because we are cumulatively intelligent creatures, whose cultures learn new and more efficient ways to shape the materials of the world to our needs. Once, we were obliged to accept only what came our way from Nature's bounty; then we learned to draw abundance from the land; now we build altogether new materials. Every year we work smarter and cheaper, with wealth increasing for all (for some much more than for others, it's true) as market signals enable us to maximise our productive powers.
The tragedy of ageing and death is that so much human effort and resource is expended in education and training that's inevitably lost within a couple of decades. Only genetic memory is transmitted more or less unblemished down the centuries, the millennia. Yes, cultural memory is compressed, shared, committed to writing and other external storage media - but its fine-grain detail perishes, in large measure, with every human who falls. We pour increasingly greater quantities of treasure into teaching first the fundamentals and then the sophisticated expertise of a thousand trades and professions and, in each case, within fifty years that treasure is wasted in death.
Suppose it need not be that way? Suppose the accumulated knowledge and, better still, the hard-won wisdom of the years were retained - not in written summary, not in tales passed down from parent or tutor to child, but in the canny brain and sinews of a vastly long-lived adult?
The dead hand of the past
Or is this, in turn, a recipe for crushing stagnation? As things are today, technical knowledge doubles even faster than human numbers. The fresh young minds of children are specially structured to take in tremendous amounts of raw and processed information, to learn new words for new ways of looking at the world. An entire generation of researchers struggles for decades to create an impossibly difficult innovative way of perceiving physics or chemistry or economics, and a pristine intake at college effortlessly gulps down that shocking paradigm shift and moves forward creatively, within what seems to them the most natural perspective. Science advances as the old bulls weaken and retire. So what happens when the old no longer weaken, when nobody is obliged to give up tenure due to physical exhaustion and slow mental decline? Is this not a return to the grim days of repressive priesthoods and principalities, when opinions are set in concrete and no disruptive new angle on the world is permitted to ruffle the timeless surface of The Way Things Are Meant To Be?
Certainly that is a risk. It is not, though, a very persuasive picture, I think. Julian Simon's market forces would surely step in to topple a rigid gerontocracy, as they are doing now in China. If the old refuse to learn, they surrender possession of the finest novelties to their rivals. Knowledge is indeed power, and new knowledge brings surprising access to new power.
Besides, must an ageless gerontocracy be rigid in this way? It is too early to know, but we might be taking a false logical step in assuming that the old in a deathless world must automatically resemble today's crusty elderly. One reason older people today tend to cling to views acquired in their own youth and early maturity is that the brain literally gives up its plasticity. The neural wiring is trimmed from the earliest months and years like a manicured topiary bush, shaped by each child's environment to create an adult well adapted to a certain historically contingent time and place. Eventually that specialisation - with its concomitant loss of flexibility - hardens into place as the ageing brain suffers damage. Neurons tangle in plaque, dying and not replaced. Yet this physical deterioration is precisely what an immortal generation will need to halt in order to forestall death. Telomerase therapy, even nanotechnological machines like hordes of clever benign viruses, will maintain the repair and health of neurons and their vast network of knowledge - indeed, of self-awareness. If mental rigidity is a risk for the deathless, it will be a psychological rather than physiological hazard, the kind that already afflicts `young fogies' who choose to squeeze their eyes shut in the face of novelty.
Hope I die before I grow old
For all that, the political consequences of massively extended youth might not be comfortable. On the one hand, a world in which everyone retained the piss-and-vinegar zeal of adolescence, in which male `testosterone poisoning' was never quenched in the hormonal ebbing of late adulthood, might be an alarming place to live. I suspect this risk can be overstated. Even diehard criminals in their late 40s or 50s are physically strong enough and brutal enough to maim and kill their foes, but it seems that they often mellow with experience. Times simply teaches us lessons of prudence that the innocence and ignorance of youth cannot know. Happily, we also learn `people skills', learn to ignore the foolish herd-mentality of the young, learn courage in taking chances that once might have frozen us solid in terror of imaginary consequences. To retain those skills in a body unhurt by the years - ah, `Bliss it was in that dawn to be alive,' as Wordsworth did not quite say, `but to be old was very heaven!'