By far the most predominant criticism made against indefinite longevity is overpopulation. It is the first “potential problem” that comes to mind. But fortunately it seems that halting the global mortality rate would not cause an immediate drastic increase in global population; in fact, if the mortality rate dropped to zero tomorrow then the doubling rate for the global population would only be increased by a factor of 1.75 , which is smaller than the population growth rate during the post-WWII baby-boom.
Population is significantly more determined by birth rate than by death rate, simply because many people have more than one natural child.
This means that we should not see an unsustainable rise in population following even the complete cessation of death globally for a number of generations. We will run into problems 3 or 4 generations hence – but this leaves us with time enough to plan for overpopulation before we’re forced to resort to more drastic solution-paradigms like procreation-bans and space colonization.
Moreover, there are a number of proposed, and in some cases implemented, solutions to existing, contemporary problems that can be utilized for the purpose of minimizing overpopulation’s detrimental effects on living-space and non-renewable resource constraints. These contemporary concerns include climate change and dependence on non-renewable energy sources, and they are only increasing in the amount of public attention they are attracting.
While these concerns and their potential solutions were not created by overpopulation or with overpopulation in mind, the potentially negative effects of an increasing global population can be effectively combatted all the same using such contemporary methods and technologies.
Thus we can take advantage of the solution-paradigms developed for such contemporary concerns as climate change and dependence on non-renewable resources, and borrow from such movements as the sustainability movement and the seasteading movement, so as to better mitigate and effectively plan for the negative repercussions of a growing global population caused by the emergence of effective longevity technologies.
In a session with The President’s Council on Bioethics (as it was composed during the Bush Administration), S. Jay Olshansky  reported calculations he performed indicating that complete cessation of the global morality rate today would lead to less population growth than resulted from the post-WWII “Baby Boom”:
This is an estimate of the birth rate and the death rate in the year 1000, birth rate roughly 70, death rate about 69.5. Remember when there's a growth rate of 1 percent, very much like your money, a growth rate of 1 percent leads to a doubling time at about 69 to 70 years. It's the same thing with humans. With a 1 percent growth rate, the population doubles in about 69 years. If you have the growth rate — if you double the growth rate, you have the time it takes for the population to double, so it's nothing more than the difference between the birth rate and the death rate to generate the growth rate. And here you can see in 1900, the growth rate was about 2 percent, which meant the doubling time was about five years. During the 1950s at the height of the baby boom, the growth rate was about 3 percent, which means the doubling time was about 26 years. In the year 2000, we have birth rates of about 15 per thousand, deaths of about 10 per thousand, low mortality populations, which means the growth rate is about one half of 1 percent, which means it would take about 140 years for the population to double.
Well, if we achieved immortality today, in other words, if the death rate went down to zero, then the growth rate would be defined by the birth rate. The birth rate would be about 15 per thousand, which means the doubling time would be 53 years, and more realistically, if we achieved immortality, we might anticipate a reduction in the birth rate to roughly ten per thousand, in which case the doubling time would be about 80 years. The bottom line is, is that if we achieved immortality today, the growth rate of the population would be less than what we observed during the post-World War II baby boom.
We would eventually run into problems, of course, a century down the road, but just so you know the growth rates would not be nearly what they were in the post-World War II era, even with immortality today.
In other words we will only have increased the doubling-time of the global population by a factor of 1.75 if we achieved indefinite longevity today (e.g. a doubling time of 140 years in 2000 compared to a doubling time of 80 years). This means that we will have two to four generations worth of time to consider possible solutions to growing population before we are faced with the “hard choice” of (1) finding new space and resources or else (2) limiting or regulating the global birthrate.
An alternate study on the demographic consequences of life-extension concluded that “population changes are surprisingly slow in their response to a dramatic life extension”. The study 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,” concluding that “even for very long 100-year projection horizon, with the most radical life extension scenario (assuming no aging at all after age 60), the total population increases by 22% only (from 9.1 to 11.0 million)” and that “ even in the case of the most radical life extension scenario, population growth could be relatively slow and may not necessarily lead to overpopulation.” . The total population increase due to the complete negation of mortality given by this study is significantly lower than the figure calculated by Olshansky.
Finding innovative solutions to new and old problems is what humanity does. We have a variety of possible viable options to increase the resources and living space available to humanity already. Moreover, there are several other contemporary concerns that are invoking the development of technological and methodological solutions that can be applied to our own concerns regarding the effects of overpopulation. Surely we can conceive of optimal solutions to these problems (and the more pressing a given problem is, the more funding it receive/s and the faster it is accomplished) – and take advantage of the growing methodological and technical infrastructure being developed for related and convergent problems – within the time it will take to feel overpopulation’s effect on living space and resources.
We could, for instance, colonize the oceans [3, 4, 5], drawing from the engineering, construction techniques used to build, maintain and safely inhabit contemporary VLFSs (Very-Large-Floating-Structures). 75% of the Earth’s surface area is, after all, water. This would increase our potential living space 3-fold – and I say potential because we surely don’t currently maximize living space on the 25% of the Earth’s surface occupied by land. Furthermore, humanity has as yet barely ventured beyond the surface of the earth – which is a sphere after all. There is nothing to prevent society building higher and building deeper. Indeed, with contemporary and projected advances in materials science and structural engineering, there is no theoretical limit to the height of structures we can safely build – the space elevator being a case in point. And while there will indeed be a maximum size wherein building higher becomes economically prohibitive (a limit determined to a large extent by the materials used), contemporary megastructures  indicate that very large structures can be built safety and cost-effectively. Underground living [7, 8, 9, 10] is another potential solution-paradigm as well; underground structures require less energy, are protected from weathering effects and changing temperatures to a much greater extent than structures exposed to the elements, and are less susceptible to damage from natural disasters. Furthermore, there are a number of underground cities in existence today , with existing techniques and technologies used to better facilitate contemporary underground living, which we can take advantage of.
In fact, the problem of limited living space is a contemporary problem for certain nations like Japan, and active projects to combat this growing problem have already been undertaken in many cases. This means that there will be an existing host of solutions, with their own technological and methodological infrastructures, which we can benefit from and take advantage of when the problematizing effects of growing global population become immediate. Not only can we take advantage of the existing engineering-methodologies developed for use in the construction of VLFSs, but we can also take advantage of the growing body of knowledge pertaining to megastructural engineering and even existing proposals for floating cities [12, 13, 14, 15, 17, 18]. Another possible solution is artificial islands .
Furthermore, in recent years the topic of Very-Large-Floating-Structures [21, 22] has experienced a surge of renewed interest occurring in tandem with the increasing interest in seasteading [23, 24], – that is, the creation of very-large-floating-structures for reasons of political sovereignty as well as to allow corporations to get around the laws of a given nation by occupying an area outside of exclusive economic zones. This renewed interest can only increase the amount of attention and funding these concepts receive, in turn increasing the viability of VLFS-design and their underlying structural-engineering and energy-production concerns.
Another contemporary movement that will prove advantageous for our own concerns with the effects of overpopulation on living-space, working-space and resource-space is the growing green movement and sustainability movement. The problem of resource scarcity is already upon us in many areas, and there exists contemporary motivation for finding more resource-efficient ways of making energy and producing goods, and for lessening our dependency on non-renewable energy sources. Climate change has only become an increasingly predominant concern in international politics, and many incentives exist to lessen our dependence on non-renewable energy sources as well as to lessen the environmental impact of contemporary civilization, which is itself another oft-touted problematic-concern possibly resulting from overpopulation. Developments in these areas are only set to continue, for reasons wholly unrelated to the effects of overpopulation, and when those effects come to the fore we will have a collection of existing methodologies that can then be harnessed to lessen the impact of overpopulation on living space and resource scarcity.
The predominance of these problems, as well as the amount of attention and funding they are expected to receive (and thus the viability of their potential solutions), will only increase as we move forward into the future. The solutions we have to the potential problems of overpopulation – namely resource scarcity and lack of living space – will not only increase as the effects of overpopulation get closer, but the technological and methodological infrastructures underlying those solutions will also become more tried, tested and robust, fueled by contemporary concerns over decreasing living space, climate-change and resource scarcity.
While space colonization is the most frequently-proffered technological solution to the possibility of future overpopulation, I think we will turn to various Earth-bound solutions to increasing humanity’s available living space, as well as the space available for agricultural labs, that is the manufacture of food-stuffs, or indoor farming systems [25, 26, 28], before colonizing the cosmos becomes an economically-optimal option. I think these sorts of solutions will be employed long before humanity if forced to either regulate the birthrate or move into the cosmos.
Moreover, people who wish to have children will have incentive to support politicians running on policies promoting new solutions to decreasing living-space. Consider the number of U.S. taxpayer dollars spent during the Space Race, with no immediate material or scientific benefit (other than to prove it could be done, as well as to maintain rough militaristic equality with the USSR to some extent, as the state of rocket technology was indicative of the state of ballistic technologies like missiles). If humanity is forced to choose between having children and receiving the medical treatments that will keep them from dying, surely people will be motivated to fund initiatives and projects aimed at solving the problems of decreasing living space and increasing resource-constraints due to a growing global population.
It is important to remember that the largest increase in life-expectancy we have experienced historically was followed by a drastic decrease in birthrate over the next few generations thereafter. Before the industrial revolution, English women had on average 6 children. In 2000 the average was less than 2.
Figure 1: English Fertility Rates in England, 1540-2000
Note: GRR = Gross Reproduction Rate, NRR = Net Reproduction Rate
Source: Wrigley et al. (1997) p. 614. Office of National Statistics, United Kingdom.
The drop in birthrate following the industrial revolution has several causes. Chief among them is the fact that children were considered to some extent as assets, helping with maintaining the family livelihood, often by doing agricultural work on a family farm or to help with household chores (which were much more extensive then). Another large determining factor is a high rate of child mortality; thus families would have multiple children in anticipation of losing some to death. But with a rise in living conditions, the child mortality rate dropped drastically – and as a result we stopped having more kids in anticipation of some of them dying. Moreover, we started treating children less as assets and more as people to nurture and raise for their own sake. Longer lives, and less susceptibility to death in general, appears to have made us better parents.
Thus it is not only possible but probable that we will see a similar drop in the birthrate as a consequence of a significant future increase in average lifespan, with people having children much later in life, when they are more financially stable and when they have done all the commitment-free things they’ve always wanted to do. Without a looming limit on one’s available reproductive lifespan, there will be no pressing motivation to have children “before it’s too late” – and this alone could very well facilitate an unprecedented decrease in the Total Fertility Rate (TFR) of the global population.
Evidence indicates that the drop in birth rate was neither limited to England, nor an isolated result of the Industrial Revolution. A net drop in the TFR seems to be a longer-term trend concurrent across the globe. It is likely that the drop in the TFR is due to the same factors as the drop in birth rate following the Industrial Revolution – increasing life expectancy and continually-improving living conditions allows people to have children without expecting a portion of them to be lost to child, to have them for the sake of having children rather than as assets to aid in maintaining the family livelihood, and to have children later in life due to the increase in one’s reproductive lifespan that comes with increasing life-expectancy. The fact that the drop in TFR is not an isolated historical event is advantageous because the global population is affected by birth rate much more than by the mortality rate. Hence we may see a continuing decrease in the TFR occur in tandem with increasing life expectancy, leveling out the imbalance created by a mortality rate of zero by a larger than has been heretofore anticipated.
Let us suppose, for a moment, the worst: that indefinite longevity is achieved and we completely ignore (i.e. fail to plan for) overpopulation until its effects start becoming readily apparent. Even in this seeming worse-case scenario, overpopulation is not likely to result in any great tragedies. In such a case we would be forced to limit the global birthrate until we are able to implement the solutions that would allow us to sustainably procreate again. If people have a strong enough desire to continue having children, then they will express their demand and politicians will consequently base their policies upon deliberative initiatives to increase available living and agricultural space – and get elected if the desire to freely procreate is strong and widespread enough. Failing to plan for overpopulation will simply be a wake-up call, letting us know that we should have been planning for its effects from the beginning, and that we had better start planning for them now if we want to continue to freely procreate.
Thus while overpopulation is the most prominent and most credible criticism against continually-increasing lifespans, and the one that needs to be planned-for the most (because it will eventually happen, but it will lead to sustainability, resource and living space problems only if we do nothing about it), it is in no way insoluble, nor particularly pressing in terms of the time available to plan and implement solutions to shrinking living-space and resource-space (i.e. the space occupied by resources such as food, energy-production, workplaces, etc.). We have a host of potential solutions today, ones we can use to increase available living space without regulating the global birthrate, and decades following the achievement of indefinite lifespans to consider the advantages and disadvantages of the various possible solutions, to develop them and to implement them.
So then: wherefore from here? Overpopulation is still the most prominent criticism raised against indefinite longevity, and if combatted, it could lead to an increase in public support for the Longevity movement. You might think that the widespread concern with overpopulation due to increasing longevity won’t really matter, if they turn out to be wrong, and overpopulation isn’t so insoluble a problem as one is inclined to first presume. But this misses a crucial point: that the time it takes to achieve longevity is determined by and large by how widespread and strongly society and the members constituting it desire and demand it. If we can convince people today that overpopulation isn’t an insoluble problem, then continually-increasing longevity might happen much sooner than otherwise. At the cost of 100,000 deaths due to age-correlated causes per day, I think hastening the arrival of indefinite longevity therapies by even a modest amount is somewhat imperative. Hastening its arrival by one month will save 3 million lives, and achieving it one year sooner than otherwise will save an astounding 36.5 Million real, human lives.
Thus, we should work toward putting more concrete numbers to these estimates. How much more living space can be feasibly created by colonizing the oceans? How deep can we really dig, build and live? How high can we safely build? Is there a threshold height or depth where building higher or deeper becomes too economically-prohibitive to be worth the added living, working or resource-space? What are the parameters (e.g. material strength/cost ratio, specific structural design) determining such a threshold?
First, we need to collect and analyze the feasibility studies that have already been undertaken on floating cities, artificial islands, VLFSs and the new solution-paradigms that are emerging to combat the contemporary concerns of sustainability and resource scarcity. In short, we need to compile data from the feasibility studies that have already been done, and the projects already implemented. Then we need to plan and commission further feasibility studies, undertaken by engineers and geologists, to build upon the work already accomplished in feasibility studies pertaining to existing designs for floating cities and other Very-Large-Floating-Structures. We need to put some numbers to the cost the additional space for food, resources, work and living-space necessitated by widely-available life-extension therapies. We need to do some hard calculations to show that the effects of overpopulation are problems that can be solved using existing megascale-engineering and construction techniques and materials, safely and economically. We need to show the world that it has more space than it ever thought it had, and that such solution-paradigms as cosmic colonization and procreative regulation are neither the only ones, nor necessarily the most optimal ones. We need in short to show them that, in this case, where there’s a will there’s a way, and that the weight of waiting is too high a price to pay.
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