I have been reading a book called “The Wizard and The Prophet: Science and the Future of Our Planet” by Charles C. Mann, and I must say the book is excellent. I strongly recommend everyone read that book. But this is not a review of that book, instead we will elaborate on a topic mentioned inside the book: human population growth.

We are all aware of some doomers and gloomers who claim humans will overpopulate the earth and the powers that be will cull the population when that day comes. And we are all aware of the people who say the earth has plentiful resources, so we can house many many more people (approximately 40 to 80 billion) before overpopulation is a real issue. But from what I have read, the real debates on human population growth are quite distant from those doomers, gloomers, and naive optimists.

The gloomers are wrong about the powers that be, for reasons we will see; and the naive optimists misunderstand the variables involved, for reasons soon to be mentioned.

The axioms involved with human population growth all relate back to an old book called the Struggle for Existence that was published by a mathematical ecologist from Russia. That book really changes how we view human population growth. It’s not strictly a matter of enough resources, nor strictly a matter of overcrowding, but also positive pressures being present or absent. As another early researcher put it:

 B – E = C

B being the biotic potential for an environment, the theoretical potential for a piece of land to produce plants for shelter, for clothing, for food, and etc., E is the environmental resistances which bring down the biotic potential. And C is the actual carrying capacity.

What this means is our population growth potential is dynamic and dependent on the resistances (positive pressures) that we add or remove. Hence, the naive optimist is missing variables. And the doomer, as we will now see, misunderstands population dynamics.

In the Struggle for Existence, the author demonstrates that organisms follow an S-curve growth pattern, with a rise and a decline. He gave protozoa enough food to grow, then removed all the resistances (E, in this case), and found that they outstripped their food sources. What he concluded from this is that all populations, as he demonstrated this experiment in other organisms, will follow the S-curve to their own demise. 

In essence, what was being predicted here was something known as a Malthusian disaster: when growth in a population exceeds growth in food supply:

So, the doomers would be wrong about some powers that be, it would instead more likely be the case that failure in population control itself would instead lead to a culling; that is, due to the inability of the powers that be to control population, we are culled.

Now the S-curve gave me lots of food for thought. And that is what we will consider, so let’s now summarize and consider what are the really important questions on this topic.

We know more resources and fewer limitations leads to a higher capacity. When an environment has tons of arable land and low amounts of diseases which attack crops or humans, for instance, growth is expected to be higher. We also know lands have a natural capacity, and that populations can push beyond that natural capacity and run into a Malthusian catastrophe. For instance, humans arguably have a fixed amount of freshwater, and so it is possible for our population growth trend to exceed the levels of freshwater we currently have.  Now, some important questions.

One extremely important question, can humans change the trend? Suppose we are indeed following the S-curve shown above, and so we will at some point outstrip our food resources if we continue on the same path. Could we instead choose to stop? Rather than continue on the same trend, can we opt to slow our growth? The question of determinism and free will seem implicit in this question, but it doesn’t need to be.

Humans are plenty different from other animals, and if I had to bet on any species to break the S-curve trend, I would bet on humans. We have seen population control done in many places before. We have deliberately slowed population growth, but we have also, more recently, increased population growth – albeit less successfully (population planning). So, rather than appealing to some philosophy of mind axioms about free will, we could simply point to the discrepancies between humans and protozoa. 

Of course, others are more fatalistic and would deny the uniqueness of humans outright; they would probably respond by saying that population dynamics are absolute laws, and humans cannot surpass them. Yet I have seen mathematical determinism fail elsewhere, that is, the idea that we are determined to follow the trends on a graph – a graph which is being extrapolated from protozoans to humans. In theory, for instance, commercial flights ought to have been using more efficient engines in accordance with the empirical findings of Moore’s law; yet they have not. The reason why is due to what is being measured. 

Human preference. Moore’s law is not a law of reality itself, it’s a law which measures human behavior. Thus, if humans do not want to develop more efficient computation, then they won’t. By the same reasoning, population growth in humans is likewise a measurement of the preference for children, among other things. It seems reasonable that such a preference could interfere with any sort of projection from current data, as it has done with Moore’s law.

The point being, I understand both takes. We want to presume humans follow the same trends as other organisms, and we want natural laws for populations; yet, many mathematical models that have human preference baked into them always have plenty of examples where the deterministic trend does not hold true. Both points have some persuasive elements.

Two other good questions, how far along are we, and what does the peak look like? Assuming we are following the S-curve, what are a good set of axioms to help us determine a proper analogy between different populations. In other words, can we make the populations commensurable? And what would the peak honestly look like? There are many reports saying that, by 2050, in order for us to feed the projected population, agricultural output must rise by 2.4% annually, yet our agricultural outputs have only been rising by 0.9% to 1.6% (see the Wizard and Prophet, pages 192, 193). Is it the case that by 2050 we will run into a Malthusian catastrophe?

Based on the numbers, we might say yes. But, as the author points out, the wizards (scientists) are optimistic about research being done on rice, salt water potatoes, and other agricultural innovations. They believe rather than reaching the top of the S-curve in 2050, we could simply raise the inflection point to be higher. As one scientist puts it: “we can either increase our actual agricultural output to reach our theoretical maximum, or instead increase our theoretical maximum, which is much easier”. The reason, he believes, is because educating farmers, giving them better tools, building better infrastructure, educating citizens to waste less, is a much harder task than paying researchers to develop crops that are more disease resistant and also give a higher yield.

So, if we ask a wizard, they will say no Malthusian catastrophe will be had in 2050. Of course, in contrast, many prophets say otherwise (ecologists and environmentalists). For them, genetically modified food leads to further environmental degradation (so a higher E in our B – E = C formula). And that means, our capacity is lowered; which is to say, the more people we feed the closer we are to having positive forces such as disease, famine, and extreme weather shrink our population.

Which transitions us to another interesting question, what policies should we practice as a species to ensure equilibrium? The theoretical maximum being lifted, for now, is mostly theoretical at the moment; there are some promising innovations in genetically modified food, but genetically modified food is not yet at the point where we could feed the population of 2050. And the data shows only a 0.9% to a 1.6% increase in output annually, when we in reality need 2.4%. So, rather than betting only on science, we might want to take our best measures to ensure we don’t outgrow our food sources.

One interesting idea mentioned in the book was said by Keynes, he believed food prices should be controlled to lower demand. This has been done before, with some success, but as the author points out, modern economics is now far more complicated. There are plenty of subsidies to consider, and much of our food is also fed to animals, who we in turn eat or use for products. A simple policy like raising food prices for wheat might instead have the unintended consequence of companies adding more of a given subsidized product, and thus lowering food quality. This is not to say food pricing wouldn’t work, but it will definitely have unintended consequences.

Another popular idea is to decrease consumption. It is no surprise that modern people living in developed economies consume far more than they need. But their increased consumption comes with a trade-off: pollution. And pollution makes land less farmable. As one example, real-estate in Southeast Asia is highly consumed by buyers, yet Southeast Asia is already farming all their farmable land; in fact, because real-estate (cities) are expanding, the amount of farmable land is shrinking. So, their increased consumption is making it harder for them to meet the food demands of their future populations; hence, why scientists are trying to develop a higher yield rice.

In summary, then, the more we look into questions about population growth, the more we realize that the answers are not extremely obvious. Naive optimists ignore the fact that we can destroy the planet to such an extent that we will never reach the theoretical human population capacity of earth. And the doomers presume humans have much more control over population growth than we otherwise have. In reality, the rate of scientific development, the rate of population growth, the rate of environmental degradation all matter and must be considered. Even philosophical questions about the nature of population dynamics must be considered.

If you do read the Wizard and the Prophet, you will likely come to the belief that only time can tell, and the best we can do is try. There are far too many variables involved for a single person to have an exhaustively accurate worldview.

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