Every niche on Earth where live is possible is fully populated to maximum capacity, and has been that way since within less than 100,000 years after life was first possible. Since then, ‘moving in’ has meant displacing the current inhabitants, in process Darwin declared “survival of the fittest”.
Is it easy to overlook that environments not fully occupied by “us” are always already fully occupied by “others”.
This is an exploration of how all environments becomes fully populated, how humanity has our current population and what we have needed to displace to get this far, and need to display to continue to displace to continue population growth.
- Rules of Population Constraints on our finite planet.
- 100 doublings of population is beyond the maximum possible on Earth.
- If even 60 doublings were possible, even pandas or humans, could from 2 individuals within 3,000 years produce a population that would completely cover the surface of the Earth.
- Every living organism has had more than ample time for 100 doublings, and is normally population constrained by the limitations of a finite environment.
- Every niche for life, is full to capacity, except following catastrophes or major disruptions.
- Population growth of any species, requires environmental changes, or evolution enabling the ‘invasion’ of environment previously populated by of other species .
- Continued Population growth is only possible through continued reduction in populations of other species.
- Every species must find population stability at some point while limited to one finite planet.
- What about humans? Are We exempt from the rules?
- Human Population Growth, how does it continue?
- Alternating Times of Stability and Times of Population Growth Through Technical Evolution.
- Ignorant Displacement: Those displaced go unseen.
- History of human population: growth steps through colonisation.
Rules of Population Constraints on our finite planet
Rule 1: 100 doublings of population is beyond the maximum possible on Earth.
Since 1 million is 1,000 times 1,000 such an organism could double its population 1,000 times in a million year timeframe, but doubling population even 100 times is more than enough for any fully populate the Earth with that organism. A doubling of population 1,000 times is , and double 63 times in 63,000 years.
The ‘wheat and chessboard problem‘ illustrates how large numbers grow by repeated doubling, also known as exponential growth.
The wheat and chessboard considers doubling 63 times, in 63 steps from step 1 to step 64, doubling each step. One grain of wheat on the first square (20=1)as the starting value, leads to 2 grains on the 2nd square (21=2), 4 on the 3rd (22=4), 8 on the 4th (23=8), all the way to 9,223,372,036,854,775,808 on the 64th and last square (263). So a single living organism would result in 9,223,372,036,854,775,808 organisms after 63 doublings.
Given the total land and ocean surface area of the Earth 510,064,472 km2, and each square kilometre is 1 million square meters, the 63 steps results in 18,082 organisms per square metre of the entire surface of the Earth, which for those who do not speak metric, is over 180,000 organisms per square foot.
So starting from two humans, 62 doublings would result in 18,000 humans for every square metre of the Earth.
Not very comfortable for humans, but possible for something very small or perhaps microscopic. Allowing the 100 doubling steps would generate 2,485,275,234,437,872 organisms per square metre ( over 25 quadrillion per square foot) or 2,485,275,234 organisms per square millimetre of the entire surface of the Earth.
So 100 doublings would overrun the earth even with microscopic animals:
- 2.5 billion organisms for every square millimetre of the entire surface of the Earth, as a result of doubling 100 times.
- So 25 quadrillion organisms for every square foot of the entire surface of the Earth, as a result of doubling 100 times.
For larger animals such as humans, even filling the ‘chessboard’ is not required, as just 60 doublings would mean over 1,000 individuals per square metre of the entire land and ocean surface.
Rule 2: 100 doublings need not take very long, even for humans.
Relative to length of time life has existed on Earth, 100 doublings of even slow population grown animals does not add up to very long time, relative to planet over 4 billion years old.
Every organism must have a mechanism to multiply, or they could never have reached their current population level, or recover population level in the event of catastrophe or disruption. Past population growth can be used to calculate a population doubling time. For example, pandas have been shown to be able to increase population 17% in a decade. A 17% increase means 117 pandas for every 100 after 10 years. Since 1.17 to the power 4.5 is greater than 2, then pandas at that rate would double in population in 4.5 decades, which is a similar to the population growth rate to humans between 1923 and 1972.
The population growth rate for humans makes sense. If every couple has 5 children, which is below the historic average prior to the 20th century, and if 4 of those 5 children live to have their own children, then humans would double in population every generation, or a doubling approximately every 30 years. Just one child above replacement rate would result in a doubling every 50 years.
But a but a doubling in population every 50 years would result in 60 doublings in just 3,000 years producing more than 1,000 individuals for every square metre of the earth, which with animals the size of either pandas or homo sapiens, would more than completely cover the surface.
For perspective, humans doubling at this rate, would have resulted in 100 doublings during the time of Ancient Egypt (over 5,000 years with almost 30 centuries as the leading civilization).
The takeaway is that every living organism, even us recently evolved homo sapiens, have had far more than enough time to double in population 100 times, and overrun the earth as a result.
Rule 3: Every living organism has had more than ample time for 100 doublings, and is normally population constrained by the limitations of a finite environment.
Every organism on Earth has had far more than sufficient time for 100 doublings of it population, but no organism has reached the incredible population number that would result if they kept doubling unconstrained.
Since, in a small time relative to how long species survive, exponential population growth can exceed the limits of the size of our finite environment on Earth, for almost the entire existence of any species, the population of the species will be at the limit possible given environmental constraints.
This means every organism has normally reached constraints that limit further population growth.
Rule 4: Excepting for shortly after catastrophes or major disruptions, every environmental niche is fully populated.
The times an organism would experience unconstrained or less constrained population growth are:
- When a species first evolves, first reaches a new suitable environment, or evolves new traits overcoming prior constraints.
- Following a major catastrophe or disruption that reduced the population below previous levels.
- In the event of changes to the environment that alter constraints such as weather or climate events, or disruption of predators or competitors for resources.
As all similar environments are not necessarily connected, an organism can be new to an environment despite having existed for some time in similar environments.
When population changes are observed other a for a new species or species new to the environment, or following catastrophes or other major disruptions, the population change is as a result of changes to the constraints.
Changes to population constraints can be short term, such as weather events, long term such as ice ages and long term climate events, or the result of evolution as observed by Darwin, or evolution of technology such as stone tools, or farming.
Rule 5: Population growth of any species, requires environmental change or evolution enabling the ‘invasion’ of environment previously populated by of other species.
If every environment is fully populated, then the only way to increase population is to outcompete other species, or for the environment to expand.
Outcompeting other species requires some form of evolution, either of genetics or behaviours.
The first land plants and animals appeared about 400 million years ago, when land first became inhabitable due to the atmosphere finally having enough oxygen to block harmful radiation and provide for respiration.
Since that time, the land joined the oceans in seeing a succession of life has replaced previous forms of life, with each species that dominated a niche reaching, and then remaining at the capacity of that niche, before eventually being replaced by an improved species.
Rule 6: Continued Population growth is only possible through continued reduction in populations of other species.
The logical consequent of these rules is that growth beyond original constraints can only continue while a species can continue to partially or fully substitute for other species within their environmental niches.
Rule 7: Every species must find population stability at some point while limited to one finite planet.
Continuing to replace other species has a limit. Eventually there would be only one species.
Some species are automatically resource constrained from overpopulation. I suspect this applies to all plants, as a major resource, sunlight, cannot be ‘overconsumed’. However even a population of butterflies can reach a population level where their caterpillars consume all food in their environment, and as their food needs time to grow, this would leave no food for the next generation.
All organisms need to ensure they live sustainably, and for any organism that relies on existence of sufficient numbers of other organisms for food or coexistence, this means some mechanism to ensure they do not out compete the very organisms they rely upon.
What about humans? Are We exempt from these rules?
Human Population Growth, is it still in unconstrained growth?
It could appear that human population is still growing long after we should have reached our constraints.
With the pat t of humans can appear to have broken these rules. The theory says we humans should have reached a stable population close to 300,000 years ago, at which point population growth would stop unless humans continued to evolved to become ‘fitter’ for existing or new environments.
Yet human population growth still continues as was doubling every generation as recently as between in 1965-1972, and doubling every 50 years for half of the 20th century.
This would seem to suggest humans have never reached their limit, and our population is still growing unconstrained.
But further exploration reveals this recent growth follows pervious periods of population constraints. Homo Sapiens have existed for at least 300,000 years, which is sufficient for 6,000 doublings of population, yet if there were only 2 people 300,000 years ago, the population growth to 8 people billion now represents just 32 doublings in over 300,000 years. That would be a doubling at an average rate of less than once every 9,000 years.
To take 9,000 years to double the population requires an annual growth rate of around 0.008%. A rate so close to zero growth, that is far more likely the growth has mostly effectively zero, with occasional periods of real growth.
This means, most of the time, even the human population has had zero growth as been at a constrained level. But then, sometimes even populations that have reached a previous plateaux, experience additional growth.
In fact, looking at the history of human population growth, as far back as back as we have any data, we have never before seen population growth anywhere near the level that was seen in the 20th century.
But even excluding the recent population explosion, human population growth has extended far longer than the rules suggest, unless their has been an expansion of the environment, or evolution in some form.
Alternating Times of Stability and Times of Population Growth Through Technical Evolution.
Instead of a recent series of steps of biological evolution, humans have experienced technical evolution.
A list of some notable steps includes:
- A population expansion during the Palaeolithic age arounds 60-80,000 years ago, through “the emergence of newer, more advanced hunting technologies”, following further developments of language.
- Another growth phase at the start of the Neolithic age that from around 5,000BCE 7,000 years ago to 200BCE as farming spread to global adoption (see graph).
- The population explosion from around 1650 with the industrial age and the reductions in child mortality.
Note that even during periods of population stability, from 10,000BCE to 5,000BCE and from 200 BCE to 1600AD, there was still some population growth as humans managed to colonise more locations.
Ignorant Displacement: As Population Grows, The Displaced Go Unnoticed.
Our current society has evolved the technology to be ‘the fittest’ in almost any niches, that we can maintain a higher human population than ever before. We can also, per unit land, maintain a higher population of crops and livestock to feed us than ever before.
The downside is a history of not even seeing organisms displaced population increases are introduced.
In fact, historically even other humans displaced by humans have been repeatedly overlooked and/or underestimated. Despite that experts now believe between 10 and 16 million people lived above the Rio Grande in North America prior to Europeans arriving:
Few contemporaries agreed with Catlin’s lofty estimate [16 million] of the Indian population before contact with the white man. “Twaddle about imaginary millions,” scoffed one Smithsonian expert, reflecting the prevailing view that Indians were too incompetent to have ever reached large numbers. Alexis de Tocqueville’s cheery assertion that America before Columbus was an “empty continent… awaiting its inhabitants” was endorsed by no less than the U.S. Census Bureau, which in 1894 warned against accepting Indian “legends” as facts. “Investigation shows,” the bureau said, “that the aboriginal population within the present United States at the beginning of the Columbian period could not have exceeded much over 500,000.”How Many People Were Here Before Columbus?
Even if there were only 500,000 people before Columbus, the nature of exponential population growth tell us, that as people had been in North America for around 30,000 years, the continent would have been populated up to the level of environmental constraints. Any land mass with even 3,000 years occupation will reach the maximum population possible for that society. Yet to people from Europe, America was ‘an empty continent’. Not only did the new arrivals not understand or see that the continent would be fully populated with the current population, they even failed to recognise the size of that population.
The new arrivals failed to recognise that this ‘new world’ continent was fully populated, and that their arrival must displace those living there already. In the 30,000 years since people first arrived in America, culture in free trading European/Middle Eastern/Asian society had managed to evolve 1,000 or perhaps even 2,000 years further in terms of dominating more of the environment, increasing population density and as a result displacing other organisms. The population of many species would need to decline in order to accommodate the influence of European/Middle Eastern/Asian evolution of society.
The spread to new territory and the impact on life before that spread highlights the changes humans had over time to the environment of Europe/Middle East/Asia, displacing other species as advances made humans the most ‘fit’ for ever more niches within the environment.
Delusions Shattered And Questions Raised.
Calculating these numbers, has shattered some illusions I had previously been misled by, but has also raised some interesting questions still to be answered.
- Shattered Delusions:
- Both North America and Australia were fully populated prior to the arrival of Europeans.
- I had previously thought, as apparently did the European arrivals, that these continents were only sparsely populated prior to Europeans arriving. Realistically, any land mass continuous land mass occupied by humans for as long 3,000 years will be fully populated to the extent possible by that human society, as were North America and Australia.
- I had thought population levels have been growing because the Earth had never been populated to capacity.
- The reality is, Earth has been populated to capacity for the hundreds of thousands of years. Population increases result from changes to society that allow humans and their food to displace other species of life on Earth.
- The question that arises is, has the recent unprecedented population explosion stayed within the bounds of the population now supported by our changed society, or has the change to infant mortality created an ‘overshoot’ resulting in overpopulation and the environmental damage that follows.
- Both North America and Australia were fully populated prior to the arrival of Europeans.
- As already covered, has the population explosion resulted in overshoot?
- What does natural population constraint look like?
What is the process constraining natural population?
Consider our close relatives in the wild, chimpanzees, bonobos and even gorillas. To our knowledge, none of these animals was experiencing significant population growth prior to recent population decline due to habit loss. What stopped their population expanding, given that, like all species, their birth rates can achieve population growth where the population is lower than the constraint limit? There seems no evidence that starvation is the mechanism of population control, as we do not see a percentage of chimpanzees, bonobos or gorillas starving. If starvation was the mechanism of population control it would be everywhere throughout nature.
This topic to be further explored.
Conclusion: If it isn’t already, one day the ‘farm’ will be overcrowded.
Long before the first human walked the Earth, there was already ‘no vacancy’. For humanity to even exist, we had to outcompete and displace other living things. But is it our mission to replace every living thing possible until it is just us and the food we farm?
If our mission is to perpetually deliver economic growth as opposed to wealth per person, then yes, continual population growth is the simplest path to that mission.
However it may be that at some point, it feels like humanity is being ‘farmed’ to generate wealth for a small subset of people, at some point our farm will start to feel crowded to the point of existing like battery hens, rather than having our free range.