We have already crossed past the sustainable human population.

The problem is not of food availability. The problem is not of land scarcity. The problem is quite simply that on a planetary scale, our species has reached a big enough number that all we can no longer keep the entire species on the same page, and all of the remaining problems are those that can only be solved by the entire planet cooperating together.

Climate change for example. Climate change is real. Climate change is making life worse all around. Yet, for the most part it has been nearly impossible to reverse or even stop the process of climate change, because its the kind of problem that can only be solved by the entire planet, all the regions of the world cooperating when it comes to energy development. Right now, the share of renewable energy in total energy production globally increases by 10% per decade. It is at 30% right now. That's too low a number to be able to fix things unless the decarbonization industry also sees a massive boom at the same time, which luckily for now it is. That is to say, we will miss the worst of climate change by barely an inch, and that too only if the world keeps cooperating as strongly as it is right now year on year for the next few decades.

That's the problem. There are so many of us that the only way to fix things is at the very last minute, by hoping that every single country is going to cooperate across the planet for two to three decades on an issue.

The second problem is regarding governance. It's nearly impossible to govern and help maintain the quality of life of the entire population of the planet at our current tech level. China for example, lifted a billion people out of poverty, yet there were still 13% of its population living below 5.50 USD per day in 2020. There were just too many people to govern or provide for in the end. This problem isn't just limited to China, but extends to even the developed world. Places like the US, where people are unable to provide for the homeless or the unemployed. Somehow, man may find himself in the richest country in the world, and if he has been dealt bad cards, he may still struggle for survival every month. Truth is, it may just not be possible to provide for 8 billion people at a decent level, even by the end of the century, with our technological capabilities doubling every 3-5 years.

The third problem is that society doesn't even require the number of humans that it currently has. Anything above 100 million may be referred to as too many, as nobody is willing to invade a country with more than a 100 million people, due to the devastation and instability that would follow. Militarily speaking. A population of more than a hundred million people is good enough to secure ones own borders. From an economic standpoint, a population of more than a 100 million people is good enough to keep the economy growing year after year, well beyond the trillion dollar point without issue, as long as there is no internal instability. Societies like the US, China, and India are thus outliers, where there are more people around than there is any use for. After a certain point adding more humans to the process gives diminishing returns. Somehow the US hasn't reached that point yet, but India and China with their extremely high unemployment rate most certainly have.

The fourth problem is of keeping everybody on the same page as to ideas and values. Homogeneous societies have the advantage that they can all communicate with one another and be on the same page as to right and wrong, and how to conduct themselves and the lives to be lived. With homogeneous societies the tendency to see other people as separate from oneself also disappears, and there is more willingness to help ones own community which is everybody around you. Today, we have a large enough global population that it is nearly impossible to keep them on the same page even when it comes to general values. It took decades to centuries of active effort by the international community and global pressure to ban slavery across the planet. Today, we still haven't been able to ban marital r*pe across the world. The west has made the most inroads when it comes to westernizing other culture, such as how Saudi Arabia is now allowing music to be taught in schools, and is continuing to liberalize over time. However, even the influence of the west is not enough to westernize the entire planet, as can be seen in the case of Africa and some Asian economies. Globally, we are at best advanced enough to have the global culture separate into 4-6 distinct groupings. We cannot get any more homogeneous than that with our current population numbers.

Taking these problems into account ,the question then arises, what is a sustainable population number for the world? Some thinkers have argued that the ideal number is exactly 8 billion where we can sustain the population at a decent quality of life over time. Others have argued that the precis number at which every person can have a good quality of life is around 2.5 billion people. Personally, I tend to favor the latter number. At 2.5 billion humans, it becomes nearly impossible to create the kind of problems that take us close to destroying the planet for ourselves. At 2.5 billion people our technology is definitely advanced enough to keep an eye on everybody and to assign resources to them. At 2.5 billion humans, we have a chance of recognizing each other as humans even across continents. 2.5 billion humans is a low enough number that every person can be a useful worker and every human can have a higher individual value to the state than the value they have today. Where every single human is deserving of dignity, good wages, and good training.

We have historical data to support this fact. After the black death the value of the average laborer went up and they had the option to choose who they were willing to work for, which allowed them to work for the best master who treated them well and set the new standard for how the laborer ought to be treated. Rent finally went down.

Conclusion:

There are too many humans on the planet right now. This has resulted in global crisis such as climate change, inability to govern all the people living within a state, too many unemployed humans, and too many conflicting cultures. Some people believe that 8 billion is the sustainable population number for the planet. Others put the number around 2.5 billion. 2.5 billion humans as the ideal global population makes more sense as it solves all the above mentioned problems and also ensures better wages and treatment for the average worker globally. For man to win, he must become scarce enough that his very existence is something to be valued.