Most people, including most engineers, suspect there is some relationship between the advances in transportation, communications, sanitation, and health care brought about by modern science-based engineering on the one hand, and the tremendous and rapid growth in world population that has taken place since 1800 on the other hand, when there were only an estimated 1 billion people worldwide. Now there are about 7 billion. Something happened beginning a couple of hundred years ago that had never happened before in the history of the world, and the effect was to make population soar at an unprecedented rate.
Whatever your opinion on whether this is a good thing or not, demographer Paul Morland has done us all a favor by writing The Human Tide: How Population Shaped the Modern World. The job of a demographer is to study the details of human population statistics: birth rates, death rates, migration, and their effects and causes in relation to economics, politics, and the rest of life. So far, so dull, you think? Not in Morland's hands.
It turns out that no matter what nation or ethnic group you're talking about, the encounter with modernity (which mainly means modern methods of transportation, communication, etc.) gives rise to what Morland and his colleagues call the first type of "demographic transition." For most of human history, population was limited both by the scarcity of food and the brevity of human life due to disease and starvation. In Biblical times, for example, nearly everyone lived on a farm, and married women typically had four or more children so that enough of them would live long enough to become useful farm hands. Everyone lived in what Morland calls "the Malthusian trap," named after the English cleric and scholar Thomas Malthus (1766-1834). Malthus said that any increase in the food supply will only tempt people to have more children, and the increased number of mouths to feed more than makes up for the original increase, meaning that near-starvation will be the typical lot of humanity into the indefinite future.
But Malthus had no way to tell that the coming century would bring with it technological improvements in agriculture (steam and gasoline tractors), transportation (railroads, automobiles), public sanitation (clean water, sanitary sewers), and health care (improved pediatric and geriatric medicine), all of which enabled first England, then parts of Europe, the U. S., and other countries to escape the Malthusian trap. And it turns out that everybody escapes more or less the same way, although the timing varies from place to place.
First, falling infant mortality and increasing lifespans lead to a tremendous boom in population, as women keep having those four or six children they've always had, but most or all of them now survive to adulthood and live much longer lives, into their fifties or sixties. After a generation or so, especially if the cultural setting encourages literacy and advanced educational opportunities for women, they stop having such large families. The means by which this happens is something of a mystery, as it involves decisions and behavior that are not easily observed on a mass scale. But in culture after culture, country after country, even in religions as different as Christianity and Buddhism, the first demographic transition works more or less the same way.
Once the average family size comes down to replacement level (typically about two and a fraction children), some countries move on to what Morland calls the second demographic transition: a further reduction in the birth rate below the replacement level. This does not immediately result in an overall population decline, because large numbers of young women may still be growing into childbearing age, immigration into the region may be significant, and many other factors can intervene as well.
But in some cases such as Japan, the birth rate is extremely low, the overall population is declining, the median age is among the highest in the world, and it is estimated that up to 30,000 elderly Japanese die alone in their homes every year, giving rise to a whole industry that specializes in removing abandoned bodies.
This is not necessarily the fate that all modern industrialized countries face. Some countries such as Sri Lanka seem to have stabilized themselves at a comfortable balance with replacement-level birth rates, reasonably long lifetimes, and a fairly constant population figure. But every country that encounters modern technology eventually goes through at least the first demographic transition.
The book also made me wonder what relationship should obtain between the way large groups of people behave on average, almost regardless of culture or faith, and the ideals of certain faiths, particularly Christianity. Morland points out that the universality of demographic transitions happens because nearly everybody (a) would rather live longer than die young, and (b) wants the same for their children, however many there are. So when the technical means become available to achieve these ends, a society adopts them, and eventually quits having six or eight kids per family unless there are extremely strong cultural or religious reasons to keep doing so. Morland does mention exceptions such as the Jewish Haredim ultra-orthodox sects and Christian groups such as the Amish, who tend to have large families whatever their circumstances are. But unless such convictions become widespread in the general population, it's unlikely that large families will become the norm in modern industrialized countries.
Is that a moral failing? Admittedly, there is a wide spectrum of opinion or conviction even within Christianity, ranging from liberal groups that favor abortion rights to conservative elements of the Roman Catholic Church that look not only upon abortion, but on any form of birth control other than "natural family planning" (formerly known as the rhythm method) as sinful. So in one sense, it depends on who you ask.
What Morland taught me is that while demography isn't all of destiny, it does have a lot to say about the histories and trajectories of regions, countries, and even continents. Sub-Saharan Africa, for instance, is the only place where the majority of countries are still undergoing their first demographic transition, with extremely fast population growth that has not yet been dampened by that mysterious collective decision to have fewer children per mother. Whether countries such as Nigeria end up managing their transition well and stabilizing like Sri Lanka, or whether they get mired in the chaos and civil strife that seems to accompany having lots of young unemployed men in your population, is a question that remains to be answered.
But when the answer comes, people like Paul Morland will have helped us understand how the invisible hand of demography contributes to history in general, and the history of technology too.
Sources: Paul Morland's The Human Tide: How Population Shaped the Modern World was published in 2019 by Public Affairs Publishing, New York.
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