The PDF version can be read here.
And the video version can be watched here:
In this essay, I will make the case that demographic transition theory is wrong.
Demographic transition theory (DTT) proposes that people go through a transition from high fertility to low fertility as their societies modernize. Supposedly, this will lead to a stable or declining world population at some point in the future. This assumption is built into UN population projections.
DTT fits the evidence of recent history. Over the last 100 years, fertility rates have fallen dramatically as modern civilization spread around the world. Today, most parts of the world have low or declining fertility.
What caused this change in human behavior?
The generally accepted view is that poverty causes high fertility, and thus alleviating poverty causes lower fertility. According to this view, poor people choose to have more children either to help on the farm, or to care for them in old age. They also have extra children to replace those who die young. If poverty is alleviated and childhood mortality is lowered, people will choose to have fewer children.
This view is rather strange. It assumes that people have children based on rational economic calculations, and that those choices are mostly based on concern for their own welfare, as if children were a means to an economic end, rather than vice versa. It does not make sense biologically, psychologically or economically. It also doesn’t fit the evidence of history.
It isn’t biologically plausible, because life forms are shaped by evolution to reproduce. Thus, abundant food should cause population growth, not population stability or decline. And that is what we observe in nature. An expansion of the food supply causes population growth for every other species. There is no theoretical reason why humans should be exempt from this general principle. Also, there have been human population explosions in the past, when food production increased.
It isn’t psychologically plausible, because parents don’t view their children as economic assets. We evolved to reproduce, not to accumulate wealth for its own sake. Parents invest much more labor in having and raising children than they could ever get back. Likewise, it is implausible that parents have extra children to compensate for child mortality. Would you have more children if you believed that they were likely to die young?
(see the rest of the post in the link)
There are several dubious assumptions there.
The first is that fertility decline is caused mostly by birth control. The problem is, it began long before birth control became widespread. A century ago, most developed nations had TFR somewhere between 2 and 2.5.
The second is that high fertility memes are durable. But usually exactly the opposite happens, "cultural change causes lower fertility" is the same as "high fertility memes lose". That happens with religious groups the same way - Mormons used to have much higher fertility, and now they don't.
As for adapting for deceases - that is a survivor bias. For example, several dozen amphibian species are believed to be wiped out by fungal infection in last decades. It is rather unlikely that humanity will go extinct that way, if anything there are some isolated tribes. But industrial civilization can collapse due to low population long before natural selection would cause fertility to rise again. With TFR 1.2 (like in Italy now) population would drop below 100 million in about three centuries.
That's not true either. It may not be feasible to achieve below replacement fertility using only pre-industrial birth control technology. It would definitely be difficult to achieve that and produce sufficient birth control for hundreds of millions of people without industrial technology.
Regardless, new birth control innovations still increased both the availability and effectiveness of birth control, which still contributed to lowering birth rates. All birth control methods have pros and cons, and when people have more options to choose from, it becomes e... (read more)