Science & Technology

Radical Life Extension and the Problem of Malthusian Hells

Is living longer in an overcrowded world better than the alternative?


"How dare you do this research? The earth is already being raped by too many people, there is so much garbage, so much pollution."

Ten years ago, an anti-aging researcher described this hostile reaction to her work in the pages of The New York Times. Not much has changed since then. The first objection one hears when one advocates radical life extension is that it will produce a Malthusian Hell of overpopulation and resource depletion. Objectors clearly believe it would be immoral to make it possible for lots of people to live to be, say, 150 years old. But is that so? Two newish papers from two controversial philosophers take on that reasoning, and tear it apart—with the help of their pocket calculators.

Philosopher John Davis from the University of Tennessee takes a direct approach, arguing that pursuing life extension—even if it results in a Malthusian Hell—is the moral thing to do. In his article, "Life-Extension and the Malthusian Objection," Davis accepts for purposes of argument that the moral goal is to maximize total human welfare over time. To illustrate how one might decide whether or not a society should permit research and deployment of life extension technologies, Davis assumes a population of two types of people: Lees and Seans. Lees who want to live a long time are 17 percent of the population and Seans who prefer shorter lives are 83 percent. Seans live an average of 100 years, while Lees using life extension treatments live an average of 600 years. Then you add up the life years of a population of 100 Lees and Seans, and find that 17 Lees would enjoy a total of 8,500 life years while 83 Seans enjoy only 8,300 life years. Treatment prohibition would result in the loss of 200 life-years, thus reducing the total human welfare possible. So Davis concludes that counting aggregate life-years rather than individual lives is the way to decide whether or not to go with life extension treatments.

Davis then considers what might happen in situations where people are forced to choose between life extension and reproduction, as opposed to a world where they can opt for both. Davis divides a hypothetical population of 100 people into three policy categories: Free Choice; Forced Choice/Treatment; Forced Choice/Reproduce. Free Choice allows everyone to choose life extension no matter how many children they have. Under a Forced Choice policy, people must choose between having children and receiving the treatments. Davis assumes a population of 100 will contain 31 Free Choicers, who take both the treatments and reproduce, 19 Forced Choicers who take the treatments and do not reproduce, and 50 Forced Choicers who refuse the treatments and choose to reproduce. The numbers reflect his own rough intuitions about how human preferences would play out. Adding up the life-years at stake:

Free Choicers 31 x 500 years = 15,500 life-years

Forced Choice/Treatment 19 x 500 years = 9,500 life-years

Forced Choice/Reproduce 50 x 100 = 5,000 life-years

In this scenario, the Free Choicers' preferences that would result in a Malthusian world trump the combined preferences of those who choose long lives over reproduction and short lives in favor of reproduction.

What drives Davis' calculations is the concept of total utilitarianism which aims to maximize utility across a population based on adding all the separate utilities of each individual together. "So far as the total net good for humans is concerned, the most justified social policy is the one that satisfies preferences over the greatest number of life-years, all else being equal," argues Davis. One implication of total utilitarianism is that "we should create as many people as possible in order to maximize the total amount of desirable experiences." Total utilitarianism might result in Malthusian consequences because a large, relatively miserable population might well have a greater total amount of utility than a smaller, happier population.

Davis' allocation of preferences among Free and Forced Choicers is based on his own guesswork, and tweaking the numbers could produce different outcomes. But no matter how you slice the numbers, it would be immoral to stop research on life extension technologies simply because of fears that they would result in a Malthusian Hell. As Davis notes, people who choose the treatments would obviously not consider living in an increasingly Malthusian world a fate worse than death, and "therefore they would probably not consider it a fate worse than non-existence for their children either." And Malthusian Hells may be self-limiting. "Will there come a time when the Malthusian conditions reach a level of such crisis that people are better off not extending their lives?," asks Davis. "Perhaps so; if they see it that way, they will stop choosing life-extension."

Is there any way to break out of this dismal total utilitarian calculation? Bioethicist Russell Blackford argues yes.

In the second new paper, Russell Blackford from Monash University in Australia specifically addresses Princeton University bioethicist Peter Singer's claim that it is immoral to want to live longer, say by doubling one's life expectancy to 150 years. Why does Singer think this? Singer begins by setting up a thought experiment in which researchers develop a pill that will double life expectancy to 150 years. He assumes that people have an average happiness level of 5 out of a possible 10 during the first 75 years. The life extension pill maintains its users at about the same level of health and mental acuity as a healthy 60-year-old for the next 75 years, reducing their happiness level to 4 for that period. This yields an average happiness level of 4.5 over the course of their 150 year life spans. Imagine Singer's pill as a kind of Fountain of Prolonged Middle Age.

Singer also assumes population control measures stabilizing population at replacement levels. As we shall see, the population stabilization assumption is a bit of a contradiction for Singer. Ultimately in the Singer scenario, the total number of people who would be born will be half of what they otherwise would have been during any specific time period without the age-retarding drug. So a long lived society might constitute 1 billion individuals and a normal life expectancy society would number 2 billion at any one time.

To illustrate Singer's calculus, Blackford does a little happiness math in his recent article "Moral Pluralism Versus the Total View: Why Singer is wrong about radical life extension." The hedonic calculation for long lifers would be:

4.5 units of happiness x 150 years of life x 1 billion individuals = 675 billion happiness years.

The computation of pleasure for short lifers:

5 units of happiness x 75 years of life x 2 billion = 750 billion happiness years.

Singer acknowledges that individual long lifers would have better lives (4.5 hedonic units x 150 years = 675 total units) than individual short lifers (5 hedonic units x 75 year = 375 units). But the total sum of happiness over any specific period of time is higher in the society without the life extension treatment. So Singer concludes that the moral thing to do is to stop research on life prolonging drugs.

But imposing population control measures should be morally suspect to someone who advocates maximizing total utility over time. Why? As Blackford points out, Singer's utility logic leads to the irresistible "conclusion that a sufficiently large population with people whose lives are barely worth living would be a better outcome than a much smaller population of people who are very happy." This is what philosopher Derek Parfit called the "repugnant conclusion." Parfit never believed that he had resolved the paradox at the heart of a total utilitarian calculus that leads to the repugnant conclusion. One consequence of this line of argument is that people should have as many children as possible in order to maximize the total amount of happiness just so long as they could eke out some minimal amount of pleasure. In fact, it would be immoral for people to restrict the number of children they bear because they would be reducing the overall amount of possible happiness in the world.

To counter the total utility logic, Blackford offers another thought experiment in which a benevolent, but not omnipotent deity has the choice between creating a world with 1 billion happy people (6 hedonic units on average out of 10 possible) versus another world with 6 billion fairly miserable inhabitants (1.5 hedonic units on average). Total average happiness on the second miserable planet would exceed that of the first by a ratio of 3 to 2 over time (9 billion units versus 6 billion units in any given year). Singer, if he followed the logic of his argument, would advise the deity to create the second world rather than the first. Blackford counters, "We expect a benevolent god to be concerned about how well lives go, rather than about the sheer number of them." The upshot of this analysis, according to Blackford, is that "what we value…is that whatever actual lives come into existence should go well."

Blackford's benevolence scenario, like Singer's original set-up, implies that the maximization of utility under Malthusian conditions will be avoided because population growth will be kept in check. However, Blackford, unlike Singer, is morally consistent, because advocating benevolence does not require maximizing total utility, but rather the goal is to attempt to maximize the utilities of individuals. As Blackford concludes, "Since I see no doubt that the lives in the pro-drug scenario would be better—something that Singer also thinks—then we should develop the drug." Of course, if one accepts Blackford's conclusions, the question of how will population be controlled comes to the fore. Will some "benevolent decision-maker" impose something like a replacement fertility requirement in order to make sure that the Methuselahs are not overcrowded thus enabling their lives to go well? Perhaps such "benevolent decision-makers" are unnecessary.

Turning from philosophy to the empirical, it is noteworthy that the societies with the longest life expectancies now are already experiencing below replacement fertility largely without the interference of "benevolent decision-makers." In addition, human ingenuity can avoid producing a Malthusian Hell by expanding available resources to more comfortably support a larger, more prosperous, and happier human population.

At one point Davis acknowledges, "Of course, if the Malthusian consequences of total utilitarianism are a reason to reject total utilitarianism, then one can argue that Malthusian consequences are a reason to reject Free Choice." Blackford implicitly accepts this analysis and rejects Free Choice. In any case, the conclusion from either analysis—Davis' dismal total utility calculus and Blackford's benevolence argument—is that pursuing radical life extension is the moral thing to do.

Ronald Bailey is Reason's science correspondent. His book Liberation Biology: The Scientific and Moral Case for the Biotech Revolution is available from Prometheus Books.