One Finite Planet

One Finite Planet

Paradox Resolved: Educating women didn’t end the Population Explosion.

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Why Population growth even before the explosion?

Throughout history, although no other species on Earth has experienced such long term overall population growth, even before the recent population explosion, the human population kept slowly growing.

Yes, we recently had an unprecedented population explosion, driven by is hidden by by the near elimination of previously tragic infant mortality, but against the background of long term growth, many of us never didn’t even realise their was an explosion.

But what drove population growth even before the explosion? What will now happen as the explosion ends?

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Population Explosion: What happened to get to 8 Billion people?

Humanity has just experienced a population explosion. Whether you believe we are overpopulated or not, the facts are that we have just had a population explosion.

Over two centuries of population peaking at 50x higher than the long term population growth, and peaking at 100x higher during the baby boom.

Yet the explosion occurred with women having less babies than ever before, even during the baby boom, and is ending all by itself.

So what caused the boom, why a population explosion when birth rates are falling? Will our population grow until we are living life like battery hens?

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Peak Child: When, and what does it mean?

Globally, the when is now. Although locally, experiences differ by location.

Data now clearly confirms that globally, the world has returned to ‘peak child’, a precursor to a likely return to peak population, and the end of three centuries of a population explosion.

Return to peak child means we could either return to the gradual growth levels of prior to the industrial revolution, or become a mature species, and exist in balance with nature and other living things. Perhaps even stop displacing other species?

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Surprisingly, humanity is at 'peak child' and looks to be heading to population stability and perhaps even 'leaving peak population' and correcting to a lower population.

We still have an overpopulated planet, following the population explosion, but the explosion is ending, due to 'births' per woman falling from over 6 prior to 1900, and to around 2.3 in 2021.

There is much confusion over why birth-rates are falling, with "education of women" often mistakenly given as an explanation, but no, the Taliban are not onto something, and rather than this or other common coincidence theories, it seems far more likely people are motivated to have the number of children that are appropriate for the situation.

Paradox Resolved: Educating women didn’t end the Population Explosion.

Surprisingly, humanity is at 'peak child' and looks to be heading to population stability and perhaps even 'leaving peak population' and correcting to a lower population.

We still have an overpopulated planet, following the population explosion, but the explosion is ending, due to 'births' per woman falling from over 6 prior to 1900, and to around 2.3 in 2021.

There is much confusion over why birth-rates are falling, with "education of women" often mistakenly given as an explanation, but no, the Taliban are not onto something, and rather than this or other common coincidence theories, it seems far more likely people are motivated to have the number of children that are appropriate for the situation.

Surprisingly, humanity is at ‘peak child‘ and looks to be heading to population stability.

We still have an overpopulated planet, following the population explosion, but the explosion is ending, due to ‘births’ per woman falling from over 6 prior to 1900, and to around 2.3 in 2021. Economists panic that and perhaps humans could even ‘leaving peak population‘ and correcting to a lower population.

When analysing the population explosion, it seemed the fall in birth-rates was a paradox as popular explanations like the “education of women” and other coincidence theories simply don’t fit all the data. No, the Taliban are not onto something, and it seems the economist nightmare is real, and people are motivated to have the number of children that are appropriate for the situation.

Synopsis: Instinct, not education of women, ends our explosion.

Births per woman from a sample group of developing countries.

Yes, around the world, birth rates has fallen.

This page, which is part of a journey to understand population, looks at three main types of explanations for the decline in birth rates which came at time when it was needed.

There are countless studies of population trends, but in the end, many explanations for the fall in birth rates just don’t add up.

The period during which birth-rates fell, was during a population explosion far beyond anything previously seen in human history, and thus the fall came just in time.

Most explanations offered for the fall in birth rates can be grouped as “coincidence theories“, as they effectively assume it was just a lucky coincidence that the circumstances triggering the fall in birth rates, just happened to occur at time when humanity urgently needed birth-rates to fall.

For example, while the education of women is sometimes suggested as a factor in falling birth-rates, that would mean that to educate women prior to the fall in infant mortality would have seen a total collapse in the human population. If education of women does supress birth-rates to current levels, then with poor medical facilities in Afghanistan it could even make sense to limit the education of women. But the truth is, that like other “coincidence theories“, while there may be motivation to want to believe it is true and apply confirmation bias, and there may be some contribution from these factors, but when considering all the evidence contributions are minor.

Population planning is not the answer either, as we know that birth-rates have fallen by very similar levels in most countries, despite most countries not having any population planning initiatives. Population planning initiative have had mixed results, sometimes resulting in birthrates almost identical to neighbours without any initiatives, and while almost having less impact than expected, in some other cases making a contribution, but never a sole explanation.

So, having been able to rule out coincidence and intervention playing the major role, the only remaining explanation is that people have responded to the growing population by reducing their own birth-rates.

The implication that some people do not want to consider, is that if the population may actually fall if people feel we are overpopulated.


The birth-rate falling any earlier would have been disastrous.

The population explosion beginning in around 1650 is evidence that child mortality rates had already started to fall in 1650, but it is not until around 1750 that there are medical records of the improvements.

Data we have from pre-1650 suggest the “births per woman” throughout most of history was around 7 children. As explained separately, this is the number expected for a woman who is healthy throughout her fertile years, and as not everyone enjoys that outcome, average family sizes may have been lower, but as some people have no children, some families needed to be much larger to maintain averages.

Despite the higher “births per woman” at 7, the overall mortality rate resulted annual population growth, as noted by “our world in data” of an average of only 0.04% from 10,00BCE to 1700CE. Further examination reveals growth was initially as low as 0.01%, and then slightly higher at 0.066% from 1000 BCE until around 1650CE. Overall, that average is 50 x lower than the peak of population explosion for the entire history prior to the population explosion.

But what would have happened, if something, as is suggested results from educating women, began in 1,000BC and did lower birth rates? If birth rates were lowered to 3 births per woman, still higher than births per woman globally today but with the mortality rate of the time, then in just by 500BCE the population would have fallen to just 200 people globally. If birth fallen fell even to 5 births per woman, then by the year zero there would have been on 2,000 humans on Earth.

Any significant fall in birth rates prior to the reduction in infant mortality, would have seen the human population collapse. If educating women is the cause of the fall to the birth rates 2020, then any society without modern medicine would be doomed by the education of women, and conversely, any society with modern medicine and uneducated women would experience record population explosions. Historical data for societies with differing religious groups having different education practices proves that neither applies, and birth rates fall with declining infant mortality independent of religion.

The explosion was an unfortunate side-effect of improved medicine.

Humanity has just experienced a population explosion. While there are various factors that enabled the explosion to continue, there is one single clear reason why the explosion happened. It was not increased birth rates, which actually fell during the population explosion. Birth rates fell, and at no time during the explosion reached pre-explosion birth-rates, even during ‘baby-booms’.

The difference between the time of population explosion, and the time before, is that during the time before the population explosion over half of all children died before growing up to have their own families. Once we solved the huge historic problem of half of all children dying before becoming adults, almost all children then went on to have their own families, driving a population explosion.

There are people who explore theories such as how improved farming allowed supporting an increased population, and factors such as these explain how societies managed to sustain the increased population, but it not the cause of the increased population. Given that birth rates did not increase, it is clear that is the advances in medicine that caused the explosion, and improved farming that prevented catastrophe as a result of the explosions.

The medical science that has reduced human infant mortality and dramatically reduce the tragic loss of young lives could be considered one of humanities greatest achievements. If the population explosion has resulted in overpopulation, that would be an unfortunate side effect of a great achievement.

The population explosion was an unfortunate, accidental side effect of saving children’s lives. It is an ‘accident’ in the sense that we did not pre-plan the population explosion, it was just a side effect that, without something bring the resulting growth rate to an end, could have ended civilization.

The explosion ends due to decreased ‘births-per-woman’.

At their peak during the 20th century, population growth rates reached 2.1% annually, or 42 times the average of the previous 12,000 years. At that rate, the same increase in population as had occurred the previous 12,000 years, would happen in just 200 years. Such a rate of increase would quickly completely overrun the planet if continued, but now births per woman has startlingly fallen back to levels similar to those previous 12,000 years. Population growth is back to the historic normal.

Births per woman, which has already began falling prior to 1960, in the 60 years to 2020, fell from over 5.0 to around 2.3. Why did the births per woman then fall? Was it another ‘accidental’ side effect of something else as with the start of the explosion?

How did the explosion end just in Time?

How many times in movies is the bomb diffused with just moments to spare before there would have been a disaster?

The ending of the population explosion in some ways seems just like those movies. In the 1970s, at the peak of population growth, many people were already predicting disaster unless something was done.

If, instead of this fall in birth-rates taking place at the time it did and the growth at the rate 2.1% per of the 1970s had continued, the 3.7 billion population of 1970 [1] would have already grown to 11 billion people today (2021), in place of the less than 8 billion in 2021. This would have been a near double increase in the world’s population over that period. Already 8 billion exaggerates every environmental problem. If population had instead grown by near double to 11 billion, what would the world now be like? Imagine CO2 levels now in a world with double the population. Plus, accelerated deforestation to access resources for over twice the number of people, and all those mouths to feed.

It could be argued that the population explosion should have ended sooner, but it seems quite clear that had the explosion needed much later, or not ended at all, humanity and the entire planet would have even worse problems right now.

[1] 3.7 x 1.02151 ≈ 11

All theories have a long human history as a source of test data.

There is a lot of data. In addition to historical population growth rates, broken down by time period here, we know that following either catastrophe or reaching new territories, human societies experience population growth higher than normal, and “normal” is near stable levels of population.

Coincidence theories: suggesting a fall unrelated to population.

Correlation is not causation: Confirmation bias, or just ignorance of history?

Many theories on the fall in birth rates make the mistake of considering contemporary events to be “normal” and assume the very atypical population growth of the 1950s to 1980s to be “normal” and overlook just the full scope of change in society during the fall in birth rates.

Commonly theories find factors with correlation with the fall in birth rates that provide a good news story if correct, and then apply confirmation bias when considering other evidence, and completely fail to even try to apply the theories to historical data.

So yes, the idea that the education of women brings birth rates down to levels practical with modern developed economies with modern health care, can provide an argument supporting the worthy cause of educating women around the world, but that doesn’t automatically make it the correct answer, anymore that the corollary if this theory is correct then educating women in societies without modern medicine would cause population collapse makes the theory wrong.

The real test is does the theory also fit with historical data, so in that case, the test would, were declines in population experienced in societies that included some education for women prior to the reduction in infant mortality? The problem is the failure of this test.

Negative confirmation bias: The economists’ worst nightmare.

Just as there are som theories that some people want to believe, there are also ideas that some people just do not want to accept.

Anyone who believes in indefinite growth in anything physical, on a physically finite planet, is either mad or an economist.”

Attributed to Kenneth Boulding in: United States. Congress. House (1973) 

Economists and economic journalists generally do not want to accept that, at least in “successful economies”, population growth will even end.

What’s more, China faces some long-term challenges, such as a population crisis, and strained relations with key trading partners such as the United States and Europe. The country’s total fertility rate, the average number of babies a woman will have over her lifetime, dropped to a record low of 1.09 last year from 1.30 just two years before, according to a recent report by state-owned, citing a study by a unit of the National Health Commission.

China’s economy is in trouble. Here’s what’s gone wrong

Time after time, any suggest population growth will in any country is reported as a “population crisis”.

This means any theory that suggests population may stabilise or even undergo a correction will meet with staunch opposition for some groups would believe there is sufficient financial motivation to invest in discrediting such theories.

The common proposals: The Pill, Education, Working Women etc.

A common explanation is that a variety of factors have in combination been responsible for reducing birth-rates. Going through the factors, most of them were not planned to reduce population growth, specifically:

  • Education of Women, which started even before the population explosion, was not motivated by a need to reduce population.
  • Increased participation of women in the workplace did not happen in order to reduce population either.
  • Even the pill, a new contraceptive, was not invented primarily to reduce population growth.

The challenge to accepting that a variety of factors resulted in the reduction of birth-rates, is that it provides no explanation beyond luck for the reduction in birth-rates resulting in population balance, or for the factors responsible for the reduction just happening to occur at the right time to for the balance, neither to early, or too late.

Just imagine if all these factors, such as educating women, the invention of the pill, increased participation of women in the workforce happened before infant mortality was so dramatically reduced? In that case, the population would have crashed as births were previously at replacement level, so there would been significantly insufficient births! Or alternatively, if the delay between reducing infant mortality and these factors reducing births had taken longer, the peak explosion could have gone another 100 years resulting in 8x the current population.

This “variety of factors” requires the balance being achieved neither too late nor too early simply being a lucky coincidence.

Population History.

The requirement of coincidence can be overlooked, if it assumed the population growth seen at the time of the reduction in birth rates had been in place for hundreds of years. While an examination of the history of population quickly makes it clear that the growth had not been in place for hundreds of years, not everyone looks. Once you look, it also becomes clear that the rapid growth prior to the reduction in birth-rates was unsustainable.

This means, accepting the ‘variety of factors’ explanation, requires either:

  • Ignoring the history of population, and previous almost stable population.
  • Or, accepting the coincidence of the factors happening at the right time and rate.

“The Pill”: A Key Factor In The Balance, Or Maybe Not?

Did the availability of the “pill” cause the fall?

Note that the fall in birth rates from 6.0 in 1900, to 4.7 in 1950, is the similar to the fall after 1950 when the pill was released.

There were many charts at one time showing the strong correlation between the availability of the pill in the USA and a strong correlation to decline birth rates. The was the issued of why birthrates fell before the pill, and while the correlation was sound for a short period after the introduction of the pill, market saturation of the pill in many countries was reached quickly, and birthrates continued to fall. Note a similar correlation exists for the USA between the uptake of colour television and decline in birth rates, plus a similar timeline for the decline in birth rates occurred in some other countries where the contraceptive pill was restricted, or the introduction delayed.

The pill was not invented by a company planning to solve the world’s population crisis. The market was families wanting control over family size, and families only wanted control over family size when they had already made the choice for smaller families. Interestingly, prior to the population explosion, humans had almost the exact balance of children required to be in balance with parents, once infant mortality took its toll. This means that had the pill been available prior to the reduction of infant mortality, and the pill did achieve a reduction in children at that earlier time, the human population would have declined following the introduction of the pill.

During the population explosion, there was certainly a market for the pill. Perhaps during this time there was an increased appetite to also reduce family sizes? How much the pill has changed when people have children compared to how many children, is hard to know.

Overall it is clear not all reduction was due to the pill, but the introduction did very likely accelerate the process.

Given the invention was not in response to population growth, then to whatever extend the pill has reduced family sizes and population growth, the pill becoming available at the right time was certainly lucky. Much earlier, and there was no reduction in family sizes needed, much later and overpopulation could be far more serious.

The Full List Of Factors.

Here is a list from ‘our world in data’ of factors linked to the change in the number of births per woman.

Empowerment of women
Women’s labor force participation
Increasing well being and status of children
Increasing prosperity and structural transformation of the economy
Culture and norms
Family planning (Untargeted)
Religion and fertility
Family planning (Targeting having less children as in Bangladesh)
Coercive policy interventions [As with the “one Child Policy” in China”]
Fertility is first falling with development – and then rising with development


Note none of the top entries were measures targeting reduction of birth-rates. This section is targeted at those reasons, and yes, there are measures directly designed to target birth rates in the list, but these are discussed further in ‘planned responses’.

This is not my list, but the list from ‘our world in data’. I would change ’empowerment of women’ to ‘education and empowerment of women’, although when I follow the link, it does become clear they do associate ’empowerment’ and ‘education’.

These ‘explanations’, can be divided into three categories:

  1. Actions specifically intended to reduce birth-rates. (see planned responses)
    • Family planning (Targeting having less children as in Bangladesh), Contraception as part of targeted programs, government programs to reduce births.
  2. Changes/actions which target other outcomes but do also anticipate reducing birth-rates, or sometimes are targeting birth rate reductions.
    • Family planning (Untargeted), Religion and fertility, Contraception (simply providing a method for avoiding unwanted children together with sexual freedom)
  3. Changes/actions with no intent to change to birth-rates an not the intent, and are not a planned outcome, but may be a bonus.
    • eg, Women’s labour force participation, Increasing well being and status of children, Increasing prosperity and structural transformation of the economy, Culture and norms

As already covered, the vast majority of countries have not taken any steps intended to reduce birth-rates, so the first two classes of explanations have already been ruled out as a universal explanation. Coercive policy interventions as applied in China, family planning that also targets population growth, as practiced in Bangladesh, can have an impact, but there are too many counties with no such measures for these to explain it all. Improved contraception has also had an impact, but again simply does not explain the extent of the change.

This leave only class number three, factors not are not designed to reduce birth rates, as the only explanations capable of applying in most countries where birth rates have fallen.

It has nothing to do with sperm counts or the usual things that come to mind when discussing fertility.

Instead it is being driven by more women in education and work, as well as greater access to contraception, leading to women choosing to have fewer children.

In many ways, falling fertility rates are a success story.

BBC- Fertility rate: ‘Jaw-dropping’ global crash in children being born

This quote from the BBC represents a typical attempt to explain the falling birth-rates. A combination of factors, but with changes to society, not at all intended to reduce birth-rates at least partially responsible for a “success story”.

Birth-rates having been reduced by side-effects, puts the reduction of birth-rates into the same category as the reducing child mortality triggering population growth: a predicable but unplanned accident.

The implication is that if we had a society where, if religion or some other factor delayed the globalisation of education of women for years, or we had not invented the pill at the time we did, our society we would probably have collapsed due to overpopulation.

If, as is generally proposed, changes/actions which predominantly did not have reducing birth-rates as a primary goal, have played a critical role in preventing a catastrophe, then we have been saved at least in part by luck.

Summary: So, all explanations that are in not way linked to efforts to lower birth-rates still amount to luck that birth rates fell when needed, as above. While these explanation provide more detailed analysis, all of them share the concept that some change to society just happened to result in a reduction in birth-rates.

Can We Explain The Pure Luck: Are We Just The Lucky Ones?

If there is only one planet in this galaxy of over 100 billion stars with an advanced intelligent life form, what are the odds of being born on that planet? Incredibly low, but since only and advanced intelligent life form would contemplate those odds, the only people thinking about the odds, have already won that very lottery. In other words, unlikely as any event may be, if the event is required for our survival, that event must have happened, because we are here to think about it. So anything required for us to be alive, no matter how unlikely, happened in our past, because in order to think about what happened, we have to be on a planet where it did happen.

The same principle could be applied to the fall in birth rate. Perhaps it just happened randomly, despite it being incredibly unlikely. The only reason we are still able to contemplate those odds, is that it did happen, which enabled us to still live in a civilized society. All the people on planets were the birth rate did not fall, at a similar point in their society on their planet, died from overpopulation, and this is just another reason why we are not seeing other advanced civilizations.

Summary: It is possible that the reduction in birth rates just happened almost randomly, and just as there is no point in a lottery winner wondering ‘why me’, there is no point in wondering about birth rates, it is just chance. That we are on the planet where the lucky event happened, enables us to wonder about it all.

Birth Rates didn’t fall in accordance with planning.

While a few countries, most notably China, did launch planned responses to end the population explosion, as most countries with a fall in birth rates did not launch any planned responses, this is not serious candidate for a global explanation. Planned responses do not explain with birth-fell across the globe without most countries having such responses, which allows ruling planned responses as an explanation, but it is still a contributing factor in birth-rates falling.

A key point is that birth-rates have fallen to ‘peak-child’/stable population levels, without a planned response from humanity.

So here is what has happened from deliberate planned responses that were specifically designed to reduce birth rates. While they cannot explain global trends, measures include:

While these measures are certainly not a full explanation for global trends the include countries where no measures were adopted, planned responses have contributed to the global reduction.

There is a full spectrum possible between trying to educate people on the advantages of less children, through to the one child policy of China which went as far as mandatory contraception and sterilization in some cases for women who already had two children. In between education and the more drastic measures are financial and employment based incentives and limitations.

Certainly there were place in the world that took steps some time after 1960 in order to reduce birth rates.

  • China introduced the one child policy in 1979 after around 10 years of an earlier two child policy.
  • Various countries introduced public campaigns to encourage parents to only have 2 children, including:
    • Vietnam (1960s), Hong Kong (1970), Singapore(1980).
  • Some countries including India (2019), have introduced incentives for less children, and others (UK, 2012) have contemplated such measures,
  • Other countries have had ‘family planning’ programs, and education programs encouraging parents to have less children.
    • see Bangladesh example in Hans Rosing video here.


The one child policy was introduced in China in 1979, when world population growth rate was still close to the 1972 peak, but there is another story, which requires considering the population pyramid for China in 1978. Looking at the pyramid, at first it looks like two child policy introduced 10 years earlier , partly in response to the great famine, was starting to work, The 0-4 year population was for the 1st time in a long time, smaller now than it was 5 years ago (the now 5-9 band). But, now consider that each five year band represents the children born to the population four bars, or around 20 years earlier. The children in the 0-4 band, were mostly born to the 20-24 band, and therefore, still represented an increase relative to their parents, and as each of the next two groups to become 20-24 in 5, and then 10 years, were even larger populations, on trend, the population would again be growing. They felt they needed more!

Hence the move to a ‘one child’ policy. The pyramid of 20 years later shows there was logic to moving to the even stricter ‘on child’ policy and even despite this, and the peak years (5-9, 10-14) were again peak years 20 years later, but the pyramid is no longer so “bottom heavy”. The world population in 1978 was 4.3 billion and increased 40% to almost 6 billion by 1998. The 31% increase in China from 0.97 in 1978 billion to 1.27 billion is below that world average. At world average, China would have reached. So how many less people than the world trend in China after ten years of 2 child policy followed by 20 years of 1 child policy?

world_increase_rate x china_in_78 - china_in_98 = (6/4.3)x.97-1.27 = 0.083 billion

Today, as the population pyramid of China has been transformed from that of 1978. The people over 50, were all born before ‘child policies’, and the top of the pyramid is still the traditional shape of from the 1960s and earlier. But from age 50 down, the shape is no longer a pyramid, but the straight sided shape of a stable population, and almost half, 48%, of the population are over 40.

Overall, from 1978 until now, the population of China grew by 48% from 0.97 billion to 1.44 billion, while the world population grew 81% from 4.3 billion to 7.79 billion. If China had increased population at the rate of the rest of the world, China would have 317 million extra people. Considering growth in China was over world average before the two child policy, perhaps China could kept growing beyond the world average? It is hard to project exactly what would have happened had China not introduced the policy. Would an extra 317 million people, or more, been able to survive? If such a population had been able to survive, would would the environment of China look like as a result, and how would having so many people have damaged the economy?

Just looking at averages, the fall in birth-rates since 1972 globally have spared the world needing to support at least 3.2 billion more people. The efforts by China have outperformed the rest of the world, and that contribution by China meant that the rest of the world had to find around 10% less reduction. Without China, there could be 317 million extra people on Earth today.

The result is significant, but only explains around 10% of the world reduction in population growth. Perhaps the policy of Bangladesh and other countries can account for another 5% of the impact, but that still leaves over 85% of the reduction in birth rates down to measures not targeted at reducing birth rates. Why effective the entire rest of the world also reduced birth-rates is down to conjecture, but what is clear is there was no world-wide deliberate program as in China.

It is not even in the same category as the way the population explosion started, where although the goal of eliminating child mortality clear was not targeted at increasing population growth, it is certain that more people alive must be a consequence. Measures such as ’empowerment of women’ do may logically be a reason for less children, but does not with certainly preclude women having the same number of children. As a cause of decrease in birth-rates, it is feasible, but untestable explanation.

The biggest conundrum with all explanations that did not deliberately seek to address birth-rates, is just how co-incidental it is that these events not only produced the lucky result of reducing birth-rates, but took place and had the effect just when we needed birth-rates to be reduced.

Worldwide, the birth-rate (Niger and some other countries in Africa excepted) birth-rates fell dramatically without intervention as implemented in China, or strong education programs as with Bangladesh. Why? Is this just luck? Or something more?

Humans adjust their birth rate to the environment.

Birth-Rates Historically Have Resulted In An Amazing Stable Population.

Humans have existed for over 300,000 years with an amazingly stable population. Prior to 1650, the average annual rate of population growth was a mere 0.007% per annum.

For thousands of years prior to the recent population explosion, people had the approximately 6 children, which just happened to be the number historically required for stable population. Historically, over time the population, did ever so gradually rise, but humans were also improving the environment.

The need to have children is hard-wired into humanity, just as reproduction is hard-wired into all living things. Yet over millions of years, most plants and animals experience a population that can fluctuate, but in the big picture is amazingly stable. Might that hard-wiring be more sophisticated than we give credit, and the need to have children be tuned to have an appropriate number of children?

Consider our nearest relatives, chimpanzees and gorillas. They seem to have stable populations, without accidentally having population explosions that are unsustainable. Just perhaps, our basic instinct to have children, is also to have children in balance.

People in the past never lived in ecological balance with nature, they died in ecological balance with nature. It was utterly tragic!

Hans Rosling (see video, 19m)

The point by Hans, is that the birth rate only produced a balance once deaths were also considered. But it was in balance. Historically, humans produced the right amount of children such that, overall there was balance. Now consider, what if the system takes time to adjust, but in fact humans have now simply adjusted to this new lower death-rate, by naturally having a lower-birth rate?

Historical population levels reveal that human population historically grew very slowly. Growing so slowly requires almost exact balance between births and deaths.

Population levels did slowly rise as civilization evolved to increasingly displace nature further and further, and as human spread over the globe, but population with few rare exceptions, remained at the sustainable level for the society. Even at 1/10 the growth levels of the population explosion, in just the time of the Ancient Egypt, humans had time to completely overrun the planet. But instead, population was to stable for thousands of years.

When people first evolved from a common ancestor shared with chimpanzees, and before the invention of farming, like chimpanzees, humans would have had natural predators, and needed higher birth-rates to compensate. This means, that historical 6 children, would also have been a step down from the previous level when humans we preyed upon.

What if, the measures introduced in China were only required while people adjusted, and are no longer necessary? What if the explosion occurred because the change in infant mortality was so sudden that we humans needed time to adapt, but we are now adapting to our changed situation?

The attraction of this hypothesis is that, instead of requiring a belief that it was only coincidence that birth rates happened to fall the right amount, just when they needed to fall, it requires only a belief that it is our nature to find balance.

The one possible factor not explored in material I have found so far, is what if humans naturally reduce birth-rates when they need to?

Sure other factors affect birth rate, but perhaps regardless of other factors, humans will find a birth rate balance, at least provided nothing interferes to a level beyond our ability to adjust. History shows humans have been able to adjust birth-rates in the past, and by reaching peak child again, while the pill and other factors may have all helped, the fact that birth rates have fallen to the replacement rate suggests that human behaviour has also played a role.

On this basis, that fall in birth rate is in response to the fall in infant mortality. There is a lag, and modern society may make us slow at picking up cues, but if this is true countries with low infant mortality will find balance sooner or later.

Yes, there is correlation with many factors such as education of women, but these factors also have a strong correlation with reduction in infant mortality.

To me this seems possible. However, perhaps the instincts that while in the jungle or the savanna, could pick up signals to trigger people to having more or less children in order to maintain the balance, have difficulty adapting to pick up the signals in our modern city environments?

Nature: Instinct affects birth-rates for an ‘optimum’, sustainable population.

This explanation is based again on reproductive behaviour playing the final role in determining rate of reproduction, but instead of population stability, proposed the target is to match perceived environmental carrying capacity.

This proposal is explained in more detail in the ‘Optimum Population’, but in summary the concept seeks to explain some details not covered by an assumption of an instinct for a stable population:

  • Population must grow following disasters or a decline in numbers, as for example has happened with whales.
  • In response to changes in climate, the ideal population can either increase or decrease, and species need the ability to adjust to changing circumstances.
  • Human population did increase with advances such as the invention of farming that provided for a larger population.
  • It is easier to explain people being able to sense that population feels appropriate, than being able to sense the correct number of children for population stability.

People now make decisions to limit their family size to 2 or 3 children, and in fact some people even make the decision to be be child-free. The choices people make go beyond While women being more educated or having an increased role in the workplace may factor into some of these decisions, the choices go beyond into other factors as well. To ignore the role of a change in how many children people want to have, seems to be ignoring something significant.

A key difference with the theory that nature targets a stable population and thus humanity will remain at ‘peak child’, is that if nature targets instead an ‘optimal’, or sustainable population, then birth-rates may continue to fall, and stabilises for some time at level that results in a population correction.

There is a lot to explore before declaring everything adds up. How could the signals work in society? Wouldn’t it be logical if people are responding to environment for people in crowded areas to have less children? So many questions that require a dedicated exploration.

It does seem that the fall in birth-rates compensating for the previous fall in child mortality, provides a better explanation than just coincidence or intervention.

Conclusion: The Paradox, and ‘Optimum Population’.

In summary:

  • Programs to reduce birth-rates played a role in ending the population explosion, but on all evidence contributed no more than at best around 15% of the reduction globally.
  • Explaining the other 85% of the reduction, as being a coincidence of several factors that just happen have a side-effect of reducing birth-rates, all occurring right at the time when humanity requires birth-rates to fall, doesn’t even apply in many countries that have seen birth rate fall.
  • It seems far more likely that the falling birth rates, even in countries where governments introduce measures designed to stop birth-rate falling, is explained by people naturally adjusting the number of children to the environment.

Update Aug 2021:

At the time I first explored this topic, that none of the existing answers I had found stood up to scrutiny was a paradox.

But further consideration, and particularly exploration of just how stable populations in nature are to not complete overrun the planet in the millions of years most organisms have been reproducing, has led me to believe ‘optimal population‘ to provide the explanation.


  • 2023 August 23 : Updated introduction and synopsis, general clean-up for clarity.
  • 2021 August 30: Updated to reflect observations from exploring optimum population.
  • 2020 March 6th : 1st version.