Ever since before the Second World War, there have been people confidently predicting that the Earth has a carrying capacity.
A limit.
A number beyond which there would simply be too many of us.
The basic argument has always been remarkably straightforward.
There is a finite planet.
There are finite resources.
There is only so much food, water, land and energy available.
Eventually, the numbers must catch up with us.
And yet those predictions have consistently turned out to be wrong.
Not slightly wrong.
Wildly wrong.
Again and again, the catastrophe is postponed because human beings do something profoundly inconvenient to the theory.
They invent.
They adapt.
They find another way.
And the really interesting part is that human ingenuity doesn’t merely solve the problem in front of us.
Very often, it changes the problem itself.
A scarcity that once appeared fundamental suddenly isn’t.
A resource that seemed limited becomes abundant.
A process that required enormous amounts of land suddenly requires much less.
A technology that was too expensive becomes cheap.
A disease that killed millions becomes manageable.
A crop that couldn’t feed enough people suddenly produces several times as much.
We don’t simply solve problems.
Sometimes we solve them so thoroughly that the world after the solution is better than the world would have been if the original problem had never existed.
That is the part the carrying-capacity crowd has always had difficulty accounting for.
They see a system.
They extrapolate the system.
Then they assume the system will continue behaving exactly as it has behaved until it breaks.
But human beings don’t work that way.
And neither does civilisation.
Our biggest problems are often our biggest opportunities precisely because they break the assumptions that have kept the existing system functioning.
When everything works reasonably well, the existing system is very good at protecting itself.
It has procedures.
It has institutions.
It has experts.
It has established interests.
It has people whose careers depend on continuing to do things the way they have always been done.
And most of the time, that is probably exactly what you want.
You don’t want somebody reinventing the electrical grid every Tuesday morning.
But eventually a system reaches a point where it can no longer pretend that it has an answer.
Something changes.
The old solution stops working.
The old assumptions stop working.
The old institutions stop working.
And suddenly the people who were previously regarded as nuisances become interesting.
The misfits.
The outsiders.
The people who don’t quite fit into the existing system.
The people who can’t thrive inside it.
The people who don’t know that something is impossible because nobody has yet explained the rules to them properly.
The innovators.
The inventors.
The wildcards.
The obsessive people who will spend ten years pursuing an idea everyone else considers ridiculous.
The people willing to go out on a limb and risk everything because they believe there is something on the other side.
These people are civilisation’s escape mechanism.
They are what happens when the normal system runs out of normal answers.
And this is one of the great reasons I am profoundly sceptical of attempts to manage humanity from the top down.
Because you cannot bureaucratically manufacture ingenuity.
You can certainly suppress it.
You can make it illegal.
You can make experimentation too expensive.
You can make failure socially or politically catastrophic.
You can create an environment in which nobody is willing to take risks.
But you cannot order people to invent the thing you need.
The Soviet Union discovered this.
Nazi Germany discovered it too, although in radically different ways.
Both regimes tried to manage populations according to grand theories about how society should work.
Both were willing to use horrifying levels of coercion to impose those theories.
And both failed.
The human beings were there.
The engineers were there.
The scientists were there.
The resources were there.
What failed was the system’s ability to turn all of that human potential into sustained innovation.
Terror is remarkably bad at producing the kind of creative freedom that genuine breakthroughs require.
You can force people to work.
You can force them to obey.
You can force them to build.
You can even force them to produce impressive technological achievements for a while.
But you cannot force the unpredictable chain of curiosity, failure, experimentation, eccentricity and individual obsession that produces the next great idea.
That is why I am suspicious whenever someone tells me that we have calculated the maximum number of human beings the planet can sustain.
Perhaps we have calculated the carrying capacity of today’s technology.
Perhaps we have calculated the carrying capacity of a particular economic system.
Perhaps we have calculated how many people can live using a particular set of assumptions about energy, agriculture, transport, housing and resource consumption.
Fine.
But that isn’t the carrying capacity of Earth.
It is the carrying capacity of our current imagination.
And those are very different numbers.
The true carrying capacity of the planet may be in the tens of billions.
It may eventually be hundreds of billions.
I don’t know.
And neither does anyone else.
Because the number depends on what human beings invent between now and then.
That is the variable nobody can put into the spreadsheet.
And perhaps that is the most important variable of all.
More people means more minds.
More people means more engineers.
More scientists.
More entrepreneurs.
More obsessives.
More people who look at a problem and say, What if we did this instead?
Most of those people will produce nothing revolutionary.
Of course they won’t.
Neither do most attempts at invention.
But you don’t need everybody to be a genius.
You need enough people trying.
Civilisation is built on the tiny fraction of human beings who see something nobody else sees and then somehow manage to make everybody else see it too.
And the more human beings there are, the more likely we are to produce those extraordinary outliers.
That isn’t an argument for endless population growth.
It is an argument against assuming that population is simply a burden.
People are also the solution.
They are the source of the innovation that allows more people to live.
And they may be one of the most important mechanisms through which we solve the environmental problems we are so worried about.
There is an odd irony here.
Poor countries tend to be dirty.
Not because poor people are inherently less environmentally conscious.
Because poverty is dirty.
People burn whatever they can afford to burn.
They cook with primitive fuels.
They lack sewage systems.
They lack efficient transport.
They lack clean electricity.
They cannot afford modern waste management.
They cannot afford technologies that make environmental protection cheap.
Rich countries, by contrast, tend to become much cleaner.
Once you have enough wealth, you can afford to stop burning wood.
You can afford proper sewage.
You can afford filtration.
You can afford cleaner power.
You can afford better agricultural technology.
You can afford to protect forests because you don’t need to cut them down simply to survive.
Wealth creates the possibility of environmental improvement.
And innovation makes that wealth cheaper and more widely available.
So if the number of people worries you, perhaps don’t worry quite so much.
We are not heading toward an endless population explosion.
Quite the opposite.
We are getting remarkably close to the peak.
Birth rates are declining across much of the world.
Countries that once seemed destined to produce ever larger populations are now struggling with demographic decline.
Europe is already there.
Much of Asia is there.
China is there.
And increasingly, the same process is moving through other parts of the developing world.
India and Africa may keep the global numbers rising for a while longer.
But they won’t do it forever.
Birth rates fall as societies become wealthier, healthier, more urban and more educated.
Eventually the same demographic transition catches up with almost everybody.
And then something rather extraordinary happens.
The great human population explosion begins to reverse itself.
We have spent more than a century worrying about too many people.
We may spend the next century worrying about too few.
Perhaps that is the final joke.
The people who spent generations calculating when humanity would consume the planet may have been looking in precisely the wrong direction.
The real scarcity may not be resources.
It may eventually be people.
People to build.
People to invent.
People to take risks.
People to have children.
People to create the next generation of people capable of solving problems we don’t even know exist yet.
We are not running out of planet.
We are not necessarily running out of resources.
We are not even necessarily running out of solutions.
We may be running out of us.
And that is a rather different problem.
Perhaps we should stop thinking of humanity as a biological infestation consuming a fixed planet and start thinking of human beings as the planet’s most powerful adaptive technology.
We are messy.
We are destructive.
We are irrational.
We are occasionally spectacularly stupid.
But we are also the species that keeps finding a way out.
Every time the wall gets higher, somebody starts looking for a ladder.
And every once in a while, somebody invents an entirely new way of getting over the wall.
That is our history.
I wouldn’t bet against it yet.