Some speculations on the effects of significantly extended lifespans

((I know that this post is speculative, almost absurdly so. Bear with me.)

The idea of radically extending human life expectancy has been surfacing more and more in the media over the past few years. Back in October, I made a brief note about recent projections by demographers that, taking ongoing improvements in medicine into account, most of the children now being born in developed countries may become centenarians. The ongoing increase in human life expectancy is one of the biggest if quietest ongoing revolutions in the world, as medicine is slowly making any number of human ailments, from cancer to HIV/AIDS to the slow degeneration of the human form, treatable illnesses, while other non-medical ways of increasing the human lifespan (through caloric restriction, as an example) also show promise. In the Greek myth of Tithonus, that Trojan prince's lover Eos asked Zeus on his behalf that he be given the gift of immortality, which Tithonus did receive, but forgot to ask for eternal youth as well. It looks very much like the coming generation of human beings will not only enjoy longer lifespans but healthier lifespans as well.

Demographics come into play here via Ira Rososfky at his Psychology Today blog, where he recently posed an interesting question: "[W]hat if science advanced to the point where life expectancy took a quantum leap or we became immortal? How would we cope with all those 200 and 300-year-old people?" In an earlier post, Rosofsky wondered whether a doubling of human life expectancy would make people self-protective to the point of paranoia. If humans gained relatively immunity from the aging process but not from "accidental illness or infectious diseases," Rosofsky wondered, might humans try to avoid taking any risks at all?

Would individuals avoid contact with others for fear of illness? Would we all remove ourselves to reclusive existences living in the equivalent of a nursing home with padded walls and floors and grab bars so we could never fall and hit our heads?

Would agoraphobia become a fact of life along with paranoia and hypochondria?

I mean, if you know your life is going to be a brief candle of only seventy or eighty years, you might say: "Heck, life is short, so what difference does it make if I take some chances?"

I know you could argue that a short life should actually make us more self-protective, but consider how you would feel knowing that if you died accidentally at seventy you could be missing out on more than one-hundred years of additional life? That's where madness and paranoia might lie.

I'd argue that such paranoia isn't very different from what people experience today. Regardless, if the numbers of the (perhaps healthily and normally) superaged steadily grew, what would happen to the age pyramid, to economies, to the environment? One scientist, Leonid Gavrilov, has argued that limits to life expectancy are probabilistic rather than deterministic, and that despite lengthened lifespans populations need not rise substantially.

Psychological consequences aside, Leonid Gavrilov, in "Demographic consequences of defeating aging," (presented at the Strategies for Engineered Negligible Senescence Conference, Queens' College, Cambridge, England, September, 2009) asks: "Is it possible to have a sustainable population dynamics in a future hypothetical non-aging society?"

In computer simulations, Gavrilov concluded 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 50-year projection horizon, with the most radical life extension scenario (assuming no aging at all after age 50), the total population increases by 35 percent only (from 9.1 to 13.3 million)."

Paradoxically, the population might even decline "if some members of the society reject to use new anti-aging technologies for some religious or any other reasons (inconvenience, non-compliance, fear of side effects, costs, etc.)."

Immortal parents, if they had only one child per couple, would double the population over time. The population would not grow infinitely.

"In other words, a population of immortal reproducing organisms can grow indefinitely in time, but not necessarily indefinitely in size, because asymptotic growth is possible," Gavrilov said in an interview with Rejuvenation Research (Volume 12, Number 5, 2009).

"The startling conclusion is that fears of overpopulation based on lay common sense and uneducated intuition are, in fact, grossly exaggerated."

He adds: "In brief, we found that defeating aging, the joy of parenting, and sustainable population size are not mutually exclusive. This is an important point, because it can change the current public perception that life extension necessarily leads to overpopulation."

Much depends on the nature of fertility in this brave new world. If it's possible for people to become parents for a longer period of time--if reproductive organs retain their potency for longer, or if some technological combination like cloning and artificial wombs comes about--then their might be a longer window of fertility. Given the current tendency for fertility to be postponed, this might well allow replacement fertility to be reached even in societies marked by lowest-low fertility.

One thing's for certain: if human lifespans are significantly extended, especially but not only if working lifespans are extended, the pensions systems currently existing will be almost absurdly unaffordable. If people could continue to retire in a particular country at (say) 65, while lifespans amounted to (say) 120 years and people would be sufficiently healthy to work to 100, barring unimaginably huge increases in productivity pensions specifically and social security systems generally would need to be massively revised.

Thoughts? As I said at the beginning, this is an absurdly speculative post, but I'd be interested to see what you'd think of the situation. Don't worry: there's going to be a purely non-speculative post on this subject tomorrow.