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)
I think the main point of the essay might be wrong. It’s not necessarily true that evolution will lead to a resurgence of high fertility. Yes, evolution is real, but it’s also slow: it works on the scale of human lifetimes. Culture today evolves faster than that. It’s possible that culture can keep adapting its fertility-lowering methods faster than humans can evolve defenses against them.
The point of the essay is that fertility will eventually increase again, if enough time passes, even if that takes several generations.
It may be true that culture can evolve faster than genes, but culture is not homogenous, so I don’t think we can predict that all subcultures will evolve to adopt low fertility memetics. Eventually, the low fertility memetics and the people who practice them will slowly die out. The essay also gave examples of how the fundamentalist Muslims, the Amish, and Ultra-Orthodox Jews have some of the highest fertility rates in the world. Even if most people adopt low fertility, the most likely prediction is that the factions that have higher fertility rates will gradually replace them until they become the new majority of people.
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.
Actually, I have a few last points to say.
That’s simply not true. If you read Wikipedia and its external sources, you would learn that birth control was actually increasingly common in the developed world during the 1800s. So, it’s logically sound to conclude that increased birth control was the real reason why fertility rates declined across the developed world during the 1800s and early 1900s. Birth control practices were also generally adopted earlier in Europe than in the United States.
Also, if you ask any parent who has a child, they will testify that their birth rate was low when they were using birth control, and that their birth rate increased when they stopped using birth control. It really is that simple.
As soon as we forget that birth control was what enabled women to pursue higher education and career advancement in the first place by liberating them from childcare, it’s very easy to over-complicate all this and come up with beliefs that don’t accurately explain why fertility rates decreased over the past 200 years. Any population that deliberately avoids birth control is guaranteed to have an extremely high fertility rate in the modern world.
So yes, birth control was the true reason why fertility rates declined in the developed world in the last 200 years. Birth control was invented for a reason: to avoid overpopulation.
Well, the more precise phrase would be “fertility decline was not caused by the invention of new birth control technologies”. It is totally possible for a society to have below replacement fertility using only birth control methods available since pre-industrial era.
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 easier to pick one that works the best for their needs and desires. It also makes it easier to use multiple birth control methods at the same time, since it’s possible for one method or another to fail.
New birth control technologies in 1900s also contributed to lowering birth rates. IUDs were developed during the early and mid 1900s. Wikipedia also states that “Vasectomy as a method of voluntary birth control began during the Second World War”. Emergency contraception was first developed in the 1970s. Roe vs Wade was also passed by the US Supreme Court in 1973, which legalized abortion nationwide across the US and gave people yet another viable method of birth control. I know people who have had vasectomies, IUDs, emergency contraception, and abortions, and I can guarantee that they would all have higher birth rates if these birth control methods weren’t available to them. It simply doesn’t make sense to insist that increasing the availability and effectiveness of birth control methods did not help reduce fertility rates.
If birth control hasn’t been enabling fertility rates to decline, then what has? Birth control has existed ever since the Ancient Egyptians. However, the increasing availability of the birth control pill, other contraception methods, and the legalization of abortion during the 60s and 70s (in the US) are notable for contributing to the declining fertility rates in the US.
The essay also argues that reductions in wealth cause declines in fertility rates. In the last century, we can observe this during the Great Depression, the Great Recession, and the Covid-19 lockdowns.
No, the opposite doesn’t usually happen. For all of human history, higher fertility memes have tended to outlast lower fertility memes. Some maladaptive memes do persist, but that’s mainly because it takes a long time for them to die out. By way of analogy, smallpox maintained a TFR of 30% after millennia of infecting humans.
Now of course, the last 200 years are exceptional, since many lower fertility memes have overpowered higher fertility memes. But exceptions to the rule don’t disprove the rule, especially when the timescale has been too short since the Industrial Revolution to see how everything will eventually play out. We are living in the most exceptional times ever in all of human history.
We can think of memes using the traditions | fashions dichotomy. Eventually, the fashions will die out, after enough time passes.
Yes, that’s mainly because more Mormons are using birth control. And yes, some higher fertility memes are losing their ground to lower fertility memes, but there’s also many high fertility memes and memeplexes that still have very high fertility rates, such as the fundamentalist Muslims, the Amish, and Ultra-Orthodox Jews.
I’m worried about this too to some extent. I’ve written a list of things that could be done to boost Western fertility rates.
What population are you referring to?
If birth control hasn’t been enabling fertility rates to decline, then what has?Rising women status contributed more than everything else combined.However, the increasing availability of the birth control pill, other contraception methods, and the legalization of abortion during the 60s and 70s (in the US) are notable >for contributing to the declining fertility rates in the US.That was a continuation of trend which started more than a century before that, after temporary baby boom reversal ended.No, the opposite doesn’t usually happen. For all of human history, higher fertility memes have tended to outlast lower fertility memes.Now of course, the last 200 years are exceptional, since many lower fertility memes have overpowered higher fertility memes.The reason that happened is that communication became much easier. So it is reasonable to expect that low fertility memes will generally win for as long as the world remains interconnected.there’s also many high fertility memes and memeplexes that still have very high fertility rates, such as the fundamentalist Muslims, the Amish, and Ultra-Orthodox Jews.There were many more highly religious (and fertile) communities in the past. So the default is to expect that they will follow the same path like say Quebec.I’ve written a list of things that could be done to boost Western fertility rates.This list looks rather US-centric. Many countries, for example in eastern Europe don’t have these specific problems but have low fertility anyway. So most likely this would not help much.As the essay explained, increased birth control was necessary for that to occur. Women cannot pursue higher education or careers if they primarily work as homemakers who raise children. Birth control was necessary to liberate women from childcare if they so choose, so birth control was still the main factor that caused fertility rates to decline over the last 200 years.
Birth rates still could not have decreased if it wasn’t for increased birth control. As for the baby boom, it was predictable that birth rates would increase when society became wealthier and had endured ~16 years of the Great Depression and World War II, which both made it harder to have children.
Not quite. It would be more accurate to say that lower fertility memes have temporarily become more popular because humans in the developed world are not adapted to resisting them.
No, that’s not reasonable. Low fertility memes have failed to overpower the remaining high-fertility memes and memeplexes that I already mentioned (e.g. the Amish, fundamentalist Muslims, Ultra-Orthodox Jews, etc), and there’s no evidence or reasoning to suggest that they will.
We need to think about this more dynamically. The future is not predicted by the average behavior of people today. The future is predicted by who is reproducing today. That is the fundamental principle of evolution. What is normal today will be extinct in the future if it doesn’t reproduce.
Eventually, humans will evolve genes and memes that are resistant to the effects of birth control. As the link explains, there’s plenty of evidence that different genes and memes affect fertility rates. It’s only a matter of time before the ones that promote the highest fertility win out and become the most popular.
It doesn’t make sense to predict that. The remaining highly religious and fertile demographics have failed to decrease their fertility rates. They practice different memes and they probably have different genes. So, what happened for Christians and Hindus isn’t necessarily going to happen for Haredi Jews, Amish, or fundamentalist Muslims.
I strongly disagree. Most of the suggestions in the list are applicable to nearly all Western countries, including Eastern Europe.
Anyway, I don’t think it’s going to be productive to continue this discussion because I feel like I’m repeating myself. I’m going to stop responding, but if you have a question or an objection, it’s probably already addressed somewhere in the Population Dynamics FAQs.
Seems to me that birth control is a part of the story, but modern lifestyle is another. People spend more time away from home; at home we do homework with kids, watch TV, scroll social networks on smartphones. It’s not just reduction of unprotected sex, but also reduction of sex in general.
I wouldn’t be surprised if people had more kids during COVID, simply because they spent more time with their partners.
I disagree. I think that access to birth control is the main factor that has been affecting fertility rates because birth control is necessary to enable the modern lifestyle that you’re talking about. As a thought experiment, if all the world’s birth control instantly disappeared, then it would be normal for everybody who has heterosexual sex to have large families, especially since modern technology ensures that nearly all infants live to adulthood. I’ve written some more detailed explanations in my Population Dynamics FAQs.
Although it’s a common belief that the Covid lockdowns increased birth rates for the reason that you describe, it’s actually false. The US Census Bureau recorded that birth rates declined during the lockdowns because people became poorer. This is consistent with my theory of population dynamics. My theory predicts that people have more children when they become wealthier, and they have fewer children when they become poorer. As the linked post explains, there is a better explanation as for why there’s a negative correlation between wealth and fertility rates.