The image to the left (which I've borrowed from a website on social psychology) shows world population versus time, and has two obviously striking features. First, the number of people stayed almost constant for eons stretching into the remote past, only beginning a slow upward trend a few thousand years ago. Second, something definitively spectacular happened about 200 years ago, which has led to an explosion of human numbers that still shows no signs of abating. In strictly mathematical terms, in fact, our population looks set to become infinite in the next half century (seriously, that's what the mathematics says according to some analyses; but more on that below).
What was is that happened? Essentially, science -- and technology. Medicine and knowledge about the causes of disease. Techniques to farm more food more reliably. Machinery to travel and subdue nature. Machinery to make better machinery. Etc. But what really made that happen -- that shift from earlier agrarian lifestyles to more modern economic enterprise? Apparently, this is still a point of serious contention among historians, anthropologists and economists, raising as much debate as our likely future.
One new proposed idea comes in A Farewell to Alms, a book due out next month by historian Gregory Clark of the University of California at Davis. His thesis, as summarized in a review in the New York Times, is that
...the Industrial Revolution — the surge in economic growth that occurred first in England around 1800 — occurred because of a change in the nature of the human population. The change was one in which people gradually developed the strange new behaviors required to make a modern economy work. The middle-class values of nonviolence, literacy, long working hours and a willingness to save emerged only recently in human history, Dr. Clark argues.
To be accurate, Clark isn't actually trying to explain the surge in population, but the sudden shift in economic prosperity that, in fact, didn't hit all nations equally. Still, there's an undeniable correlation between the population explosion and economic growth; indeed, a graph of GDP per capita doesn't look much different to that of population, showing the same marked rise after around 1500-1700, clearly linked to the increasingly effective use of technology. What Clark argues is that these shifts were actually caused by some significant change in the nature of people and their social habits.
And he suggests that an evolutionary process was at work. As The Times article continues,
Generation after generation, the rich had more surviving children than the poor, his research showed. That meant there must have been constant downward social mobility as the poor failed to reproduce themselves and the progeny of the rich took over their occupations. "The modern population of the English is largely descended from the economic upper classes of the Middle Ages," he concluded.
As the progeny of the rich pervaded all levels of society, Dr. Clark considered, the behaviors that made for wealth could have spread with them. He has documented that several aspects of what might now be called middle-class values changed significantly from the days of hunter gatherer societies to 1800. Work hours increased, literacy and numeracy rose, and the level of interpersonal violence dropped.
In the language of The Social Atom, Clark claims that the Industrial Revolution resulted primarily from evolutionary change in the social atom, its nature and habits, and not as an abrupt transformation or phase transition in collective social dynamics. Of course, individual habits and collective outcomes are closely linked, but what I think he's arguing is that it was evolutionary changes in the individual, first, which triggered massive collective change, not vice versa.
Logically speaking, I can see nothing to rule out such an idea, although I also don't find it strongly persuasive. My primary objection (as someone who has not read the book, mind you!) is that Clark seems to be thinking of evolution as genetic evolution, which was certainly taking place in the human population then, as it is now, but which generally takes a long periods of time to operate. More likely would be a form of cultural evolution, in which learned behaviors ("acquired characteristics," in biological terms) get passed down through generations by teaching and habit. Cultural evolution does happen quickly; look at how attitudes about the equality of men and women, or the races, have changed in 50 years, or how the nature of children's games has been transformed in 20 years. This is the kind of evolution that transforms a world in two centuries.
But if you go over to cultural evolution, it seems to me, Clark's thesis ceases to be radical and looks a lot more like the alternative view that it was change in social institutions, i.e. in the social patterns that constrain and direct our individual lives that were most important. Pattern more than people, in the phrase I like to overuse.
I have no evidence for it, but my guess is that the industrial revolution was more in the way of a socio-technological phase transition; a gathering and multiplying of technologies and know how that fed upon itself, ultimately driving a qualitative change in social activity and organization. New technology doesn't just let us do more things, and easier, but lets us invent more new technologies. Scientific advance doesn't give us only understanding and technology, but also new ways to do science -- to learn more even faster.
But whatever the cause, we're coming to the end of that era. At least that's what the mathematics seems to suggest. A few years ago, physicists Anders Johansen and Didier Sornette looked at the data for world population growth, and found that it has actually been considerably faster than exponential; indeed, the most natural mathematical fit is a curve that goes to infinity in the next 50 years. As they put it,
Contrary to common belief, both the Earth's human population and its economic output have grown faster than exponential, i.e., in a super-Malthusian mode, for most of the known history. These growth rates are compatible with a spontaneous singularity occuring at the same critical time 2052 +- 10 signaling an abrupt transition to a new regime.
In physics, whether in quantum field theory, general relativity or anywhere else, the appearance in a theory of an infinity -- a "spontaneous singularity" -- means that the theory breaks down. It suggests that something that hasn't been operating under ordinary conditions will come into play there and keep things finite. If the mathematics of Johansen and Sornette is right, then there's another social phase transition in the near future. (Of course, you don't really need mathematics to be convinced of that.)
11 comments:
A very thought-provoking post, thank you. Of course, I haven't read the book either, but in the blogosphere, all speculation is fair...
Looking at the chart, I think one could argue that population growth began ~700 years ago, which could support a role for the Black Death. Lots of changes in European society can be traced to that catastrophe. In addition, an interesting factoid is that the death rate differed by class. Among the rich, the death toll was only about 15%, but among the poor, the death toll was high as 80% or more. That would be consistent with Clark's theory that the genes of the rich form a greater proportion of today's gene pool.
It is more difficult is to identify a genetic explanation for the genteel, middle-class-esque behavior of the upper classes; The upper classes in the 1300-1900 era were not exactly models of todays polite, non-violent, self-disciplined working stiffs. Socialization has to account for most of the variance.
But maybe mental ability could be a distal factor--the ability to solve novel problems, learn more, learn faster, deal with more things at one time. That has a biological basis. If we assume that the rich, then as now, were smarter than average, then as the descendents of the rich permeated the population, the population would become smarter. And if smarter, quicker to adopt new behaviors in order to adapt to new environments. Cultural change could accelerate.
It's interesting to read this post when last week's Economist cover article was "How to deal with a falling population", which made the claim that population growth is slowing, and world population will peak in 2050 and start to decline after that. Building on the ideas in your post, rich people tend to have fewer children and invest in them more heavily. Those norms are being exported, such that as developing countries gain in affluence, their fertility rates drop. I haven't read the Johansen/Sornette paper, but I'm going to trust the demographers over the physicists on the topic of population growth.
Eric,
Good point. No question. I actually don't think the Johansen-Sornette study is in any way inconsistent with The Economist story, or with the beliefs of demographers. Indeed, one of the points the physicists make in their paper is that as we're quite close to the transition point, we're probably already in the transition region. So the precursor changes of the phase transtion are presumably already manifesting themselves, and what The Economist article mentions are some clear examples of this (falling birthrates in economically advanced nations, for example).
I mentioned the physics work as I think it's a fascinating application of mathematical physics in an unusual setting, not because I think they're in any way doing demography better than the demographers. (Having said that, however, I do recall from my time at Nature a curious discussion I had with a colleague of mine. He'd just handled and ultimately accepted a paper that made some bold predictions about the future of population growth. After reading it, I complained to him that the paper really didn't seem to make much of an attempt to justify its conclusions. He agreed. "No," he said, chuckling, "it's just a string of assertions!"
Kate,
"In the blogosphere, all speculation is fair" -- that's nice to know!
I agree with you, Mark, on your main points. (Also without have read the book.)
There are so many complex factors that lead into the upsurge in population in recent centuries. kate's point about the Black Death is well taken. It thinned the population and changed the way that a lot of Europeans perceived the world.
Also, ancient Greek and Roman writings had been passed back to Europe from Islam and Aristotle became the Harry Potter of the Middle Ages. The first universities open, inquiries into phenomenon natural and intellectual begin to blossom. Trade routes to the east are established.
The dissemination of middle-class values would seem to be tied to the rise in mass production techniques, which, starting in Renaissance Venice, had huge effects on how and where people lived.
One of the greatest improvements brought--and one of the most underrated--was the improvement in hygiene, both personally and socially. The misery caused by the Black Death was dwarfed in both speed and magnitude by the cholera epidemic that spread westward from India in the middle of the 19th Century. The discovery that it was caused by drinking water being polluted by sewage led to the development of modern water and sewage treatment. This alone has probably saved more lives than any other single advance.
I think, though, that Marshall McLuhan's saying, "We shape our tools and thereafter our tools shape us" is inherently correct and plays into this whole phenomenon.
The information on the Johansen/Sornette paper is fascinating. I can readily believe that we are in the transition already.
Mark, Good point about social evolution (rather than biological evolution) bringing about rapid changes in short periods of time. The striking thing about the plot in your post is that it demonstrates how utterly unsustainable human activities of the recent past are. If the population saturates at some level in the next few decades, the net population growth rate will look like a sharp spike (a delta-function) spanning a couple of centuries within tens of millennia. I can think of no stable situation in which the growth rate does not essentially go to zero in the next few decades. The growth rate could, of course, undergo a sharp negative spike (due to natural or man made catastrophes), in which case the population itself would resemble a delta function.
I'm not sure I know what a delta function looks like, but I'm figuring that it isn't a pretty prospect. In fact, I'll boldly go on record as predicting that 2052, give or take 10 years, is not going to be one of the golden eras of human history.
I've seen estimates that the sustainable size of the worlds' population is around 2 billion people. Here's a sobering analysis that fleshes out the Johansen and Sornette math. How we--"we" being the world's population--get from our current population of six billion to a sustainable population of two billion may be the big ethical challenge of the 21st century.
Kate,
Thanks for that important link. This is just the kind of analysis that I think is highly important, based on investigation of biological factors and the carrying capacity of the biosphere, rather than economic impacts and such. Yes, getting down to 2 billion is not likely to be pretty.
A delta function is a spike; it's actually not a function at all (for strict mathematical types), but the limit in some crude sense of an up-and-down pulse as its duration gets infinitely short, while its height gets infinitely high, with the area under the curve always remaining equal to one. It was introduced by the physicist Paul Dirac long ago to solve some tricky mathematical problems.
Territorial expansion may be another factor. For example the Americas were very sparsely populated prior to the European colonisation.
kate wrote "How we--"we" being the world's population--get from our current population of six billion to a sustainable population of two billion may be the big ethical challenge of the 21st century," and I completely agree. Getting to a glide path from 6 billion to 2 billion in itself may not be too difficult. I think a birth rate of a bit less than 2 per couple (I'm too old/lazy to do the math) will do it in a few generations. The main challenge will be to manage and match the decreasing production and consumption rates. Could an authoritarian, socialistic system (read China) be actually better than us at manging this transition?
As the story in The Economist would indicate, there will be a lot of resistance to stabilizing population levels, let alone declining levels. Corporate marketers are not anxious to have the size of their market shrink.
Even today, we see baby bonuses being implemented in nations like Germany, Japan and Russia due to concerns about declining population leading to shrinking economies. It would be wise for us to adopt realistic expectations about the size of our economies. They should shrink to match the population, and in fact should probably shrink even more than that if we cannot get down to a sustainable population size.
Dave Gardner
Producer/Director
Hooked on Growth: Our Misguided Quest for Prosperity
www.growthbusters.com
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