Malthus, Darwin, and the (Sustainable?) Future of Humanity

Thomas Robert Malthus. (Wikimedia Commons, public domain)

In 1798, Thomas Robert Malthus, a British scholar, published (anonymously at first) An Essay on the Principle of Population. In this highly influential work on population dynamics, he noted that “the increase of population is necessarily limited by the means of subsistence.”. Put simply, a population can’t keep growing, as the resources it needs are finite. Those populations that outgrow the resources available to them, will stop growing and decline.

Darwin (top) and Wallace (bottom) on the Darwin-Wallace medal awarded by the Linnean Society of London. (Wikimedia Commons, public domain)

Malthus’ work has influenced numerous people, not in the least Charles Darwin and Alfred Russell Wallace. After all, the limits on populations growth and size, due to the finite nature of resources, mean that there will be moments when more offspring will be produced than can survive. Aha, the notion of ‘survival of the fittest’ was born. The diligent and insightful work of Darwin and Wallace, influenced by Malthus’ remarks on population growth, led to one of the most profound ideas of our age, by now amply supported by loads of evidence: the theory of evolution.

A recent article in Trends in Ecology and Evolution discusses the Malthusian-Darwinian Dynamic (MDD) and its relevance for the future of the human species.

The basic idea is this:

Malthus posited that a population tends to increase until it reaches its environmental limits.

But, evolution, or the Darwinian dynamic, can push these limits back. New traits and technologies can allow individuals in a population to use resources more efficiently, or may enable the exploitation of new resources.

Nevertheless, this MDD can only get you so far. Unlimited growth in a finite world is just not possible.

What does this mean for us, the mammal species known as Homo sapiens?

 Well, for one, our population growth has been quite exceptional. From less than a million about 50 000 years ago, to over 7 billion now. And in a few decades, so estimates tell us, we’ll probably end up somewhere between an astonishing  9 and 10 billion. This growth, unsurprisingly perhaps, has greatly transformed our home planet. But how has this been possible in the first place? One aspect of it is cultural evolution and the link between growth and innovation. Growing populations led to larger and more complex social groups, where information was shared and, subsequently new technologies developed, resulting in more efficient use of more resources.

Global human population over the last 10 000 years, with major innovations that allowed further population growth. (Source: Nekola et al., 2013)

Can this go on indefinitely? Some (aka Cornucopians) say yes. Human inventiveness and the rapid pace of technological change preclude insurmountable limits to human population growth. Others (aka Malthusians) say no. Earth possesses a finite amount of possible resources.

And, we’ve been squandering those resources. The MDD, as the authors note, often results in motives that benefit the individual, even if they do so at the expense of the population (see also, the tragedy of the commons). Further, they say, there is a lack of foresight. In other words, rather than recognize lurking environmental limits, we keep going. Finally, regardless of our ingenuity, we’ll eventually hit a wall. Creating energy or matter from nothing is, to the best of our knowledge, not possible.

So, can we keep growing the way we’re doing now? Well, I see a few options:

• The human populations crashes. We go on and slurp up resources at a pace that prohibits a ‘refill’. Perhaps this results in a decreasing pace of innovation, perhaps in a global ‘dark age’, perhaps even in extinction.

• The human population is managed sensibly (for now, let’s ignore the ethical issues implicit in that sentence). Population growth slows down and resources are managed with less short-sightedness than they are now.

• The human population spreads out. Mars and moon colonies, floating cities, interstellar ‘arc ships’, and so on. Coupled with technologies and scientific advances that allow the use of previously unavailable resources, or the much more efficient use of currently available ones, this might allow a relatively high population growth for a while. (But keep in mind that population growth is often exponential, so that won’t last that long.) Even in this option, a more prudent growth rate seems advisable.

Feel free to add your own proposals in the comments.

For me, a combination of the second and third option seems the way forward. We should be careful as we’re already overexploiting our little planet. But we should keep pursuing science and technology vigorously. However, relying on possible future developments is difficult. So, careful management together with a (full-blown?) pursuit of scientific and technological advancement appears a good route ahead. However, this requires a change in mentality.

Hopefully, we’ll be capable of it…

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Nekola, J., Allen, C., Brown, J., Burger, J., Davidson, A., Fristoe, T., Hamilton, M., Hammond, S., Kodric-Brown, A., Mercado-Silva, N., & Okie, J. (2013). The Malthusian–Darwinian dynamic and the trajectory of civilization Trends in Ecology & Evolution DOI: 10.1016/j.tree.2012.12.001