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.)