Life Extension? No Thanks

Would it be good if the average human life-span were not 75 to 80, but 150? 500? 1000?  Peter Singer raises the question in this online editorial. To get the ball rolling, let's ponder three mini-worlds.  The first world is more or less like ours, while the second and third involve longer life-spans.  In "30-90" people on average have a child at 30 and die at 90 (couples have two children).  So, starting with two people, A and B, here's how things look over time--

30-90 WORLD

year      people
0     A B
30   A B C D  (A and B have C and D)
60   A B C D E F (C and D have E and F)
90   A B C D E F G H (E and F have G and H; A and B die)
120  A B C D E F G H I J  (etc)
150  A B C D E F G H I J K L
180  A B C D E F G H I J K L M N
210  A B C D E F G H I J K L M N O P
240  A B C D E F G H I J K L M N O P Q R

Population density stabilizes at: 6 
Total people who exist in 240 years: 18

Now picture a world with longer average lifespans--say, 150 years--but the same average age of reproduction.

30-150 WORLD

year    people
0      A B
30    A B C D
60    A B C D E F
90    A B C D E F G H
120  A B C D E F G H I J
150  A B C D E F G H I J K L
180  A B C D E F G H I J K L M N
210  A B C D E F G H I J K L M N O P
240  A B C D E F G H I J K L M N O P Q R

Population density stabilizes at: 10
Total people who exist in 240 years: 18

In 30-90, people are replaced by their great-grandchildren.  In 30-150, by contrast, they're replaced by their great-great-great-grandchildren.  You can picture this vividly by imagining someone on their deathbed. In 30-90, at most there will be two generations of descendants on hand.  In 30-150 there could be 5 generations of descendants.

30-150 is an environmentally problematic departure from our world.  The increased population density means greater strain on resources.  We get something--longer life--but at a high cost.  For this reason (I imagine) Singer adds delayed child-bearing to the picture.  Now suppose people give birth at 90 and die at 150 (these mini-worlds are my invention, not his)--

90-150 WORLD

year    people
0      A B
30    A B
60    A B
90    A B C D
120  A B C D E F
150  A B C D E F G H
180  A B C D E F G H I J
210  A B C D E F G H I J K L
240  A B C D E F G H I J K L M N

Population density stabilizes at: 6
Total people who exist in 240 years: 14

90-150 is no more environmentally burdensome than 30-90, since population density stabilizes at the same level.  But fewer people exist in 240 years--4 fewer than in the other two worlds.

1/22 Thanks to a commenter I see I've made a mistake here.  I've got only the first generation reproducing at age 90. Will fix when I have a moment....

1/23  Upon further reflection--to maintain the same population density, we just need to maintain the same ratios.  People need to reproduce 1/3 of the way into their lives, as in 30-90. So we need to look at a 50-150 world.  (If people lived to 900, they'd have to reproduce at 300, etc. etc.)

50-150 WORLD

year    people
0         A B
50       A B C D
100     A B C D E F
150     A B C D E F G H
200     A B C D E F G H I J
240     no change

Population density stabilizes at: 6
Total people who exist in 240 years: 10

Will make changes below so that I'm comparing 30-90 to 50-150.

So which is the best world?  Singer seems to be open to the possibility that 50-150 could be best. There are fewer deaths from old age per unit time.  People spend less time fearing death, since the end of life is further in the future.  One downside he mentions is "the missing people"--O, P, Q, and R in my mini-model.  They exist in both 30-90 and 30-150, but not in 50-150.  We shouldn't be concerned about them, Singer seems to say--
One reason for thinking it better to have fewer people living longer lives is that only those who are born know what death deprives them of; those who do not exist cannot know what they are missing.
I'll buy that we haven't mistreated O, P, Q, and R by not creating them.  We haven't done them any personal harm, since they aren't around to harm.  But that's not the worry I would have about the 50-150 world. My worry is  about the people in 50-150, not the people left out.

But first, a word about delayed reproduction.  Singer and other life-extension advocates seem to think delayed reproduction might be in the cards. He writes--
contrary to what most people assume, success in overcoming aging could itself give us breathing space to find solutions to the population problem, because it would also delay or eliminate menopause, enabling women to have their first children much later than they can now.
I don't really understand this.  In what sense would people in 50-150 be better positioned than people in 30-90 to solve the population problem?  (Indeed, what population problem?  Population density is no greater in 50-150 than in 30-90.)  In any event,  my understanding is that menopause is not a product of aging.  A fascinating article Jared Diamond published a couple of years ago says menopause is actually adaptive.  Women go through menopause because it helps them have more descendants if they function as grandmothers instead of adding to their existing offspring.  So anti-aging research isn't going to eliminate or delay menopause. Only anti-menopause research is going to eliminate or delay menopause.

But OK, suppose we undertake both.  So we are biologically able to shift from 30-90 to 50-150.  Would we really want to? I have three misgivings--

(1)  Delaying child-bearing until 50 sounds about like putting off sex until age 50, or romance, or reading novels, or drinking coffee.  The good stuff in life shouldn't get postponed 50 years! I don't see the proposed trade here (early reproduction for delayed death) as a terribly attractive one.

(2) I think life extension advocates are mistaken about the psychology of death in old age.  They see 50-150 as preferable because, though there's just as much living going on in 50-150  (there are just as many person-hours) as in 30-90, there are fewer deaths in 50-150, and fewer hours of apprehending death.  But how do people feel as they approach death?  Surprisingly unbad. It's intriguing that positive psychology shows, quite consistently, and all around the world, that happiness over time fits a U-shaped curve.  We are happier as we  leave middle age and get closer to the end of life. My experience spending time with very old people is that they're remarkably cheerful. They are masters of black humor, and don't worry over much about impending death. So 50-150 solves a problem that may not really exist to begin with.

(3) My most serious worry is about the lower total population of 50-150.  10 people wind up existing in 240 years, in contrast with 18 in 30-90.  The reason this troubles me is not because I'm concerned about the four missing people. They are not harmed by not coming into existence.  The reason why 30-90 seems better is because it has greater human richness.  It's more diverse because eight more people come into the world, and that diversity has advantages for the people who exist in that world. Greater human diversity goes along with more intellectual and technological progress, or so it's been hypothesized by authors as diverse as Matt Ridley (the Rational Optimist), Toby Ord (see this short post, watch this video, and Cass Sunstein (Infotopia: How Many Minds Produce Knowledge).  They hypothesize that the huge current population of the world is one reason why we are at a point of unprecedented development in many areas.  More people means more specialization, more minds working on problems. The crucial thing here is not just how many people exist at a time, but how many exist over time.  Arguably, 30-90 is better than 50-150 for the reason that more people are around to contribute to the human enterprise in 30-90 (though the same number exist at one moment in time).

Now, the progress we get from large populations comes at an environmental cost.  So nobody's saying "the more the merrier (period)".  But the extra diversity of 30-90, compared to 50-150, has no environmental cost at all.  The population density of the two worlds, at any moment in time, is identical.  So by transitioning to 50-150 we'd be giving up human diversity (with probably loss of progress), and gaining nothing, environmentally speaking.

People do fear death and want more years of life, of course, so there's something attractive to most of us in the idea of anti-aging research. The talk of human diversity and progress doesn't have any power to help us face death. It's all abstraction and speculation, no consolation.  Or is it?   I actually do find some consolation in the notion that new people make the world a better place.  It would not have been for the best if our ancestors in 1500 had discovered a longevity pill, allowing them to live for 1000 years.  The cast of characters on the human stage would have been much reduced and that would have been for the worse.  I think we can take comfort in the idea of a new cast of characters coming into existence, especially if we live in such a way that we identify strongly with future people.  That way we will one day be out with the old, but we'll also (in various attenuated senses) still be in with the new (see Mark Johnston's interesting book Surviving Death for thoughts along those lines).   I think 30-90 is OK, if not perfect, and possibly quite a bit better than 50-150.


Alan Cooper said...

What *is* all this nonsense about "human richness"?

If you really believe in "the more the merrier" then why not let's all have 4 kids and double the population in a generation? The total number that the world can support in any level of comfort that is not painful is obviously limited, and there is good reason to believe that greater total richness of human experience might be achieved with a *smaller* population than we have now, let alone the 10 billion we are headed to if things level out as we hope (or the 20 billion or so we might reach before total collapse if they don't).

Jean Kazez said...

Hold on! Nobody's saying "the more the merrier". We're comparing two futures with the same environmental impact, because the same population density. The question is whether a 30-90 world has any advantages over a 90-150 world on grounds that, though equal in population density and environmental impact, one yields a larger number of people in a set period of time. The argument (which you find in highly respectable people like Ord, Ridley, and Sunstein!) is that the larger number does have benefits. This is not obvious or intuitive, but they make the case that with more people there's more specialization. 100 people each living for 200 years each cannot come up with the same intellectual innovations as 200 people living for 100 years each, because 200 people are more varied in their talents and expertise. The environmental impact is the same, so we can ignore that. The issue is whether it's better if we head for a future where more people live shorter lives or fewer people live longer lives. I think there's a pretty strong case for the former.

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Anonymous said...

" The reason why 30-90 seems better is because it has greater human richness"

why? as you correctly said the total number of person-hours is the same.

You seem to assume that letting old Einstein die to replace him with a new infant increases the "human richness". I think that's highly disputable.

We should model the way humans master complex subjects, and balance the cost of learning some material from scratch Vs the (eventual) benefit that comes from having a completely new look at a subject matter.

"They hypothesize that the huge current population of the world is one reason why we are at a point of unprecedented development in many areas", yes but that is an increase in total person-hours, so it won't help you to discriminate between the two possibilities.

Jean Kazez said...

All these people (Ridley, Sunstein, Ord) think that a large number of different people will bring about more progress than a smaller number of people living for more years. Same person-hours, but the increase in human diversity is advantageous. The reason why is because different people have different talents. To generate very complex entities like computers and rockets, you need all those different talents. It's not just as good to have a smaller number of people, and let them live a very long time. Now of course, there are exceptions. Better to have Einstein for 1000 years than 10 other people for 100 years each. But the claim is about what's true on average. On average, more people create more advancement than fewer people (assuming the number of person-years is the same). I don't think this is at all obvious, a priori, but these authors do make it quite plausible!

Wayne said...

Strictly in terms of human advancement and progress, I hthink individuals living longer would produce more progress than the alternative. We spend a quarter of our lives learning and preparing for careers. If we didn't have to reteach a new generation as often we could get more people up to speed on the problems that need solving with the mental skill set if being able to solve it.

Instead of having one person work for 20 years on a problem, then teaching someone else for 20 years to work on the problem after he does we could get 40 years of continuous work in a problem.

Diversity of ideas also spurs innovation no doubt, but I think inspiration is rather random and isn't necessarily increased in quantity with more people. Although I admit it may well be.

Aeolus said...

I think we need to define what we mean by "progress". Better smart phones and faster rockets? Is progress going to make the average person happier? More eudaimoniaful? (See William Morris's News from Nowhere.) If the longer-life scenario required cutting the present global population by two-thirds, we'd still have almost as many people around as in 1950 -- an enormous pool of diversity and intellectual capital to draw from. I vote for longer lives and slightly less rapid "progress".

Jean Kazez said...

Thanks for all the great comments. I think the basic point here is that we shouldn't overlook advantages of numerousness. There are obvious costs, but also hidden benefits--if Ord, Sunstein, and Ridley are right. There are trade offs of course...like Wayne says, if people's lives are too short, there's going to be more investment in training and education. At some point, all the advantages of numerousness are cancelled by the disadvantages of retraining... etc. But there are nevertheless advantages (often unnoticed!) of numerousness.

OK, my main point was #3, but let's not ignore #1! From a personal perspective, my main reason for turning down the 90-150 world would be that I don't think I'd want to postpone having children until I'm 90. I think that postponement would have all sorts of ill effects on life (from an individual, "eudaimonistic" standpoint--like Aeolus wants to focus on). This is another hidden consideration. It seems like we could all just live longer, and ... hurray! But longer life really does mean postponing reproduction (my mini-models show this), if increasing population density is to be avoided.

Brandon Berg said...

Putting aside the appalling cavalierness with which you dismiss concerns about the human suffering brought on by aging and death, your 90-150 model is completely wrong. You have every generation except AB reproducing at 30 and dying at 90.

To get population to stabilize at the same level as the 30-90 model, you just double both numbers. A 60-180 model, in other words.

You then end up with having only ten people exist in 240 years. But that's not a real issue. Even if we grant that this "human richness" is so important that it justifies forsaking a doubling of human lifespan, it's not necessary to do so. What really matters is not how many people have existed in a fixed span of time, but rather how many were born over the course of so many lifetimes.

The passage of time in and of itself is meaningless. In billions of years the universe will succumb to heat death, but aside from that, time is scarce only insofar as human biology makes it so. If it takes 360 years instead of 180 to produce six generations, who cares? It's still two lifetimes.

Jean Kazez said...

1) I don't dismiss concerns about suffering and death--cavalierly or otherwise. 2) You're right about the error in the third model. 3) But your solution isn't quite what's needed. The question is: if people die at 150, at what age must they reproduce, so that population density remains the same as in 30/90? 4) I'm not convinced the passage of time is meaningless. If various inventions will increase average quality of life dramatically, and this will happen in X years, it seems to be better for X to be smaller rather than larger. For example, suppose the inventions have to do with spinal chord injuries. I think it's obviously better if they come in a shorter amount of time.

Vovix said...

Your main and fatal ethical flaw is that you treat people as means for someone (you?) to enjoy how they replace each other to make life supposedly more interesting for that observer. People are not means. They are conscious living beings who can suffer or enjoy life themselves, live or die. And besides, people can find much more meanings in life than just reproducing. If you should not hurry until 90 (or more) to have children "now or never" (and then spend your time to bring them up), you will have much more freedom to explore other opportunities. Compare some underdeveloped African region where the situation is 15-45, where women are 90% illiterate, where they totally lack education and produce more babies than their weak economy can grow, and you have a catastrophe. The situation in 30-90 Europe or even some 25-75 Arab country is much better but still not perfect. The world of, say, 90-240 will be much better in terms of wisdom, education, long-term responsibility at least.