Originally published in French by AFT on April, 26, 2016. Translated: Alexandre, JMIacino
Overpopulation is both a complex problem and a legitimate concern. However, as we will demonstrate in this paper, compared with other factors, longevity is actually a negligible factor of overpopulation. In fact, increasing life expectancy could even contribute to stabilize and maybe even to reduce population growth!
We think this is important to refute that idea that longevity = overpopulation, because it is not a harmless idea. Actually, this formula is so widespread that it is used to stop investment of public money in longevity research, because people making decisions have serious reserves: nobody wants to invest money in a project that would lead to an overpopulation crisis! Therefore, it is important to avoid turning longevity into a scapegoat.
In addition, if we knew how to live much longer in good health, it would not be very humane to force people to die at 80 in order to avoid some hypothetical overpopulation problems. In the following, we will demonstrate that it would not only be inefficient, but also counterproductive!
The culprit? Fertility rate, not longevity!
The fertility rate is the average number of children per woman in a given population. When this rate is around 2, the population is considered stable. A fertility rate greater than 2 is a very common occurrence in certain countries, where women have more than 5 children per woman [1].
Intuitively, we think that a spectacular extension of life will have a much greater impact on population growth than a fertility rate slightly greater than 2. In fact, the opposite is true!
To understand this, let us consider a simple example. Assume an initial population of 1000 people. The fertility rate is 2, and the life expectancy is 80. Women give birth at 20.
Now, let us consider two variations:
Case A: Death disappears. Nobody dies anymore!
Case B: The fertility rate slightly increases from 2 to 2.5.
Which of these two cases will lead to the greater population increase?
A quick calculation gives the following results:
- After 500 years, the population will be 26 000 in case A, and at least 780 000 in case B: 30 times more than in case A.
- After 1000 years, the population will be 51 000 in case A, and at least 206 000 000 in case B: more than 4000 times case A! The gap will be enormous.
This example is very simple, and leaves many parameters aside. However, it underlines a significant phenomenon: the complete disappearance of death, however spectacular it may be, only causes a linear population increase; while a fertility rate slightly greater than 2 causes an exponential population increase.
Leaving ethical considerations aside, making people die at 80 is simply not an efficient way to prevent overpopulation. The real cause of the population explosion is the fertility rate. Being overly concerned about life extension, while easily accepting a fertility rate slightly greater than 2, is simply not rational. Even if death disappears tomorrow morning, the resulting population increase would be smaller than the one observed during the baby boom [2]. And should it happen in Sweden, then after 50 years, the population increase would only be 30% [3], which is within the limits of the population increases observed during the last century. Therefore, even after such an unlikely event (and assuming that it is a problem), we should have more than enough time to adapt. But we are far from being at this point: living 50 more years would already be a major scientific advance! There is no good reason to ban or to refuse to finance longevity research.
Population increases the most... where people have the shortest lives
There is an inverse correlation between fertility and longevity: population increases the most in the countries with the shortest life expectancy. The common cause is poverty: when infant mortality is high, there is an incentive to have many children to ensure that some of them eventually survive. In addition, when there is no retirement system, the only "retirement insurance" consists in having many children. Further, to this double incentive to have children, must be added the lack of access to contraception, and a lack of information about it.
Even in poor or developing countries, fertility rates decrease and longevity increases. In Bangladesh (one of the poorest countries in the world), between 1970 and 2010, life expectancy increased from 42 to 69 years, and the fertility rate decreased from 7 to 2.3. In Brazil, during the same period, life expectancy increased from 59 to 73 years, and the fertility decreased from 5 to 1.8 [4]. Therefore, people concerned about overpopulation should focus on reducing inequalities and improving the standard of living of the poorest countries. Indeed, according to history, these are the most efficient methods to slow down population increases!
The fertility rates of many rich countries have fallen under 2 children per woman (e.g., Germany with 1.4 children per woman) and have to use immigration to keep their population stable. In these countries, the risk is not overpopulation, but underpopulation! Further, these rich countries will probably be the first to benefit from transhumanist technologies, most particularly in the domain of longevity. Therefore, it is very unlikely that increasing life expectancy will result in an overpopulation crisis; especially since such an increase will first happen in rich countries, where the fertility rate is low.
Although in these same rich countries, living longer with a better material security theoretically allows to have more children, what happens is exactly the opposite. Keep that in mind if you think that the first human to live 1000 years will spend his/her life procreating!
Finally, keep in mind that even if we lived 1000 years, a fertility rate slightly lower than 2 (e.g.,1.9) is sufficient in the long-term to result in a decreasing population. It is already much lower than 2 in many rich countries [1], and in more and more other countries it is falling below 2. On this subject, see the very interesting conference of Dr. Hans Rosling on overpopulation:
At 10:00, a very "dynamic" illustration of the inverse correlation between longevity and fertility rate.
The end of the biological clock
Increasing life expectancy could even contribute to reduce the number of births. Indeed, nowadays, many women live under the "biological clock" dictatorship: a woman must hurry to have children, because if she waits too long, it will be too late. Thus, in doubt, better having children now than regretting it later! But a slower aging process would postpone this "deadline", giving more time to reflection. Thus, people would have children only by choice, and not by anxiety nor haste. Besides, if artificial wombs were to be created [5], this biological clock limit would totally disappear.
Further, fearing death can lead to having children for bad reasons: the fear of disappearing, the desire to create a "replica" of oneself who will accomplish what we failed... A slower aging reduces the anxiety towards death. Thus, we can assume that humans who live longer will only have children for "good" reasons: love, desire to pass on knowledge... Actually, this phenomenon is already happening, which explains the correlation between longer life expectancy and smaller number of children in many countries.
Finally, living longer allows to have children later, which also limits the growth of population. More generally, if future breakthroughs of science and medicine allow us to dilate our life agenda (death at 160 instead of 80, menopause at 90 instead of 45...), this would not change anything in terms of population at any given moment in time.
On the contrary, arbitrarily reducing life expectancy would be a cause of "stress" that could lead us to have as many children as possible before the "time" - which, as shown above, would cancel all the "benefits" of a forced death in terms of overpopulation!
The context evolves
Last but not least, keep in mind that the context can radically change before life expectancy increases significantly (as seen above, even a brutal disappearance of death would change nothing during several years). This has already been the case during the industrial revolution. We could discover new ways to provide shelter and food to more people at a smaller price, make new zones habitable, and even, in the long-term, colonize new planets.
It is evident that a radical increase in population is not a "goal" in itself. But, assuming that it happens, it's consequences may be far less dramatic than what we imagine today, because the context will have evolved. In the previous century, some people thought that London would eventually be entirely covered with horse manure. Today, this idea makes people laugh! [6]
In past predictions, we always underestimated the increase of life expectancy and always overestimated population growth. Are we not making the same mistake again? Two centuries ago, Malthus (the most famous thinker of overpopulation) was making apocalyptic predictions based on the scale of one century. Today, the population has been multiplied by 8 and instead of collapsing, the standards of life have significantly increased.
Finally, living longer will make people more concerned by overpopulation issues, and motivates them to find solutions. Indeed, should we live much more longer, and should our planet become overpopulated in the future, we would be the first to be concerned!
References
[1] https://en.wikipedia.org/wiki/List_of_sovereign_states_and_dependent_territories_by_fertility_rate
[2] “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 [1], which is smaller than the population growth rate during the post-WWII baby-boom.” ( http://ieet.org/index.php/IEET/more/cortese20131003 )
Original source: https://bioethicsarchive.georgetown.edu/pcbe/transcripts/dec02/session2.html
[3] “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).” ( https://www.psychologytoday.com/blog/adventures-in-old-age/200912/would-immortality-become-overpopulation-nightmare )
[4] “Et si on arrêtait de vieillir !” (“What if we stopped aging ?”), Didier Coeurnelle, 2012 ( http://transhumanistes.com/archives/2608 )
[5] http://ieet.org/index.php/IEET/more/Arendt20160330
[6] http://futuryst.blogspot.fr/2007/10/parables-and-horseshit.html