The question about human overpopulation is not whether there can be overpopulation, but whether the often popular claim that the earth can not sustain the current or the projected future human population is true. The latter absolutely is debatable - there's no clear evidence that it's impossible (i.e. there's no technically feasible way) to sustain the current or the projected future human population. It absolutely is true that if we maintain the current level of CO2 emissions, it won't be sustainable. But that's not an evidence for overpopulation. If we sustain the current level of pollution, it likely will not be sustainable. But that's once again not an evidence for overpopulation - as we know for most of our resources that there are technical alternatives that can drastically reduce / eliminate them. We know there's more than enough energy. We know how to make our economy carbon-neutral. Most pollution can be controlled. The urban land takes up much less than 1% of the earth land - and we expect the world population to peak around 10B by 2100 (vs 7.7B today). No reason to believe we'll run out of land. There's more than enough headroom to improve the crop yields in poor countries.

In the grand scheme of things, we - humanity - know mostly how to create a sustainable technological system that can support 10B population. Whether our politics will allow us to get to such a system is a entirely different problem, and THAT might be our undoing, but I'd argue that's not really an overpopulation problem.

Also, the population growth is largely a side-effect of demographic transition - https://populationeducation.org/what-demographic-transition-.... i.e. it's a transitional side-effect of reducing the human suffering. The only humane and equitable way to move forward is to accelerate the demographic transition (i.e. improve the economic, health, education, etc, systems of all countries in the world to get them to stage4 at least). And, thus, "keep our numbers down" is not only inhumane or inequitable, that's ineffective - the developed countries already mostly stopped growing - e.g. https://www.statista.com/statistics/1251591/population-growt... - and it's mostly the poor countries that are growing - i.e. https://www.statista.com/statistics/264687/countries-with-th... . There's no other humane way to stop poor countries' population growth - the most effective way is to improve their economy, improve their health and healthcare systems, and improve education.