I'm unsure. Basically, we tend to over-use or mis-use resources if there is no obvious incentive not to.

Archeology has now demonstrated that anywhere Homo Sapiens arrived, the population of big mammals plummeted and many were exterminated.

For example the mammoths were all killed at some point between 4000 and 1500 BC when humans were maybe a few millions on Earth.

Whales were almost exterminated at the end of the XIXe when the global population was around 1 billion (from memory).

Even the bison population was doing bad because Native Americans were far too efficient at hunting after the horse was introduced to the Americas by the Spanish conquistadors. So they tended to hunt only female bisons because their leather is thinner than the males', e.g. easier to use for clothing etc. Saying this does not absolve European immigrants for exterminating Native Americans and bisons and many other species. The issue was obvious enough then that huge Natural Parks were created at around 1900 (or even earlier, I have to check this).

The idea that ancient tribes had sustainable economies is a myth. They just had to do with the conditions of their environment and their creativity at inventing tools.

The human species is the most enduring species at running. Other species get tired much sooner. This seems weird because most of us are couch potatoes in comparison to Neolithic humans. Napoleon's armies could walk 70km per day with 30 to 40 kgs backpacks. Their bone density was twice ours.

We hunt collectively with elaborate strategies. Therefore even basic (for us today) hunting weapons were efficient enough to depopulate whole species. Add horses and we were then quite well-off. Hunter-gatherers are thought to have "worked" 4 to 5 hours per day, meaning the time spend to meet their objective needs. Life wasn't hard.

That may seem unbelievable. But, in the 50s & 60s, an husband with a good job could sustain a whole family of 5 and enjoy the American middle-class way of life (large-enough house, a car, a tv-set, health and education) ... it's almost impossible nowadays, even unbelievable. By the way, the middle class was large but the working poors, such as newly-arrived immigrants, were however numerous.

We are fierce predators by nature. When we are not killing animals, we make wars. When we have peace, a few extra dollars and time for leisure, we invent "games" where we "play" at killing each other or hunt monsters. Oh, these monsters are terrifying and more powerful than us but we are endurant. We spend evening and nights chasing them in virtual mazes rather than chanting with friends or dancing. Or watching movies with guns and atrocities all the f...g time. What's wrong with us?

Yes, being 7.4 billions makes it worse today but we have reduced our fertility only when constrained by an economic system we imposed on ourselves and onto others, humans and all living forms.

Overpopulation is not the cause of the issues. Our nature of Homo Sapiens is. Overpopulation is a consequence of our general predation on absolutely everything and everyone. Not as individuals, buy as groups. Within our group, we are gentle and nice. Hence the painting on our faces (still nowadays) and the uniforms we need to become "warriors". We need it to legitimate the violence that would be unacceptable within our tribe.

We are not overpopulated: we are just Homo Sapienses. We are the baddies.

:-/