Tuesday, September 6, 2011

110 Billion Deathless People

Damien: On Sunday, I raised the question “Must the end of death (except by accident or overwhelming infection or war) necessarily produce a vast population growth spurt?” It’s still not clear to me what the answer is, but the consensus of serious thinkers who’ve addressed this question appears to agree with me that it won’t be a major issue “for a long time—especially if many of the very long lived women are past their reproductive years.”

An interesting paper we’ll return to was published last year by the Russian husband and wife team Leonid A. Gavrilov and Natalia S. Gavrilova. Their paper, “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?” They show that in advanced societies, it’s the decline of populations that is the urgent issue, and even radical life extension for those past 60 will not bring us grief.

My point is that while men keep building new spermatozoa throughout their lives (and there are reports of men in their 90s become fathers), women have all their ova from before birth. Many eggs are pruned away by natural processes even before birth. They are obliterated at an extraordinary rate in the run-up to menarche. Then, around age 50 or so, menopause shuts down the female reproductive system as the last eggs vanish.

So if women are physiologically infertile after age 50 or 60, their indefinitely prolonged youthful life could not lead to additional babies from them. Unless radical steps are taken to implant a blastocyst into a medically prepared, hormonally rejigged uterus. This is not the kind of choice most women are eager to make, even if rejuvenation fixes routine cellular decay. It might become a choice after you’ve been alive for a century or two, and yearn to have another baby gurgling in the cot, but it seems unlikely to be widely adopted immediately by unaging but sterile women. (Just my guess; I might be wrong, and I’m biased because I have no kids of my own and don’t want any. Not yet, anyway.)

Now, this is an interesting consequence that I think is often overlooked in a too-simple calculation. I have the impression that a lot of people doing quick&dirty calcs on the impact of immortality treat it like compounding interest. But in compound interest, every existing dollar in your account contributes to future growth. That’s precisely not the case with an ageless future population of the kind I’m describing.

Let’s take the most extreme situation as a thought experiment. Suppose when Homo sapiens emerged, somewhere around 120,000 years ago, or more recently, repair and superior immunity mechanisms had evolved to complement intelligence. Imagine, then, that nobody had died, or aged beyond early adulthood, since then. Estimates of how many people have ever lived vary between 60 and perhaps 110 billion. Seven thousand million of those are now alive. So we might have lived in a world with perhaps 5 billion fertile men and woman and children yet to become fertile, plus 105 billion unaging people who do not themselves add to the increase in human numbers.

That is, the number of kids added to the Earth’s ecological load would be pretty much exactly the same as now. It’s just that there’d be 110 billion of us, rather than 7 billion. Nearly 16 times as many as now. Well, that’s a lot, but it’s not infinitely many. Still, is that even feasible, or would the world have collapsed long ago in a nightmare of resource wars, desperate crowding, and ecological despoliation?

Well, maybe not. If you’d lived for 100,000 years as a healthy 25-year old, would you necessarily be stuck digging insects out of a tree with a twig, or knapping stone? Hunter gatherers in the past century or two who entered advanced technological societies did not, by and large, remain aloof. Granted, for many it was a dreadful culture shock that destroyed their existing societies and languages, but that would not have happened in a deathless human world. Admittedly, known “primitive” cultures had truly atrocious murder rates, and maybe that would have persisted for a long time—but if so, that would have slowed the supposedly ruinous growth of human numbers. Meanwhile, we know that aggregations of people, especially cities of a certain size, tend to be the creative core of humanity. My guess is that we’d long ago have solved all the soluble problems of feeding, clothing, educating and amusing the world in as close to a Utopian way as we’ll ever manage.

If that’s true, it will come about in the same way during the next century or the next thousand years—once each of us has a realistic expectation of living indefinitely, healthy but increasingly wise with experience. And understanding, with slowly dawning horror, that it doesn’t make much sense to crap in your own nest, one you expect to live in for millennia.

The real test will be whether old minds in the new bottles of unaging flesh will retain the flexibility and joyous, infectious curiosity of youth, or will grow ever more in-turned, alienated, jaded and perhaps bitter and murderous. (“Get off my lawn, you kids!”) But long before that, I think, we’ll develop ways to tweak our own drives, to expand and edit our memories, to remain young at heart even as our bodies remain young in every other organ as well.

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