I kinda went on a little research spree on economics this afternoon but at one point I figured it’s probably good to know if it’s possible for, say, at least 98% of people on earth to live a happy fulfilled life at all.
I know there’s plenty of people who’d be more than happy to have literally nothing more than a house, food and water, but that still leaves a whole lot of people who want other things in life.
Do we have any metrics or data on wether the earth can sustain roughly 8 billion humans?
Yes and no. It really depends on what you mean by “comfortable and happy”.
There are people living in developing areas of the world who still essentially live as peasant farmers or unskilled laborors. They live on less than $2 per day, and scratch by day by day with barely enough to eat. And some of those people are happy. And many of those people live under authoritarian, kleptocratic regimes. If everyone lived like those people and was able to be happy in the same way, then yes, the earth could sustainably support the whole population we have now and more.
On the other hand, we can imagine what would happen if this was the case. Everyone is content and happy living as a subsistance farmer, and everyone has kids at exactly the population replacement rate. Well, at some point someone will notice that they like it when other people like them. Like, they really, really like it. And they notice that other people like them more when they have and do cool things that other people want to do - like travelling to Bali or riding jet skis. So they go jet skiing in Bali so they can show all their friends in Nebraska the photos and have everyone tell them how cool they are. But a funny thing happens - while they are in Bali jet skiing, they meet a bunch of people who go paragliding in France. So now they want to go paragliding in France, since they also want these people to like them.
This is the basic concept of the social heirarchy, and it is pretty much universal across human societies. In societies with extremely rigid heirarchies, you are born into your caste and know it can never change. Some people will find comfort in this (“since I can’t change it, one less thing to worry about”), while others will hate it. But in societies with fluid social heirarchies, most people find themselves motivated to move up or at least maintain their position in the heirarchy. And since even if you don’t care about moving up, when you notice others around you moving up it feels like getting left behind. And how do you signal your position in the heirarchy? Via ostentatious displays of wealth, luxury, and niche social knowledge. Via this mechanism, the total resource consumption of humanity would gradually rise until something stopped it.