Indeed, when we lived in caves, there were only so many of them. We totally blew past the cave sustainability model thousands of years ago.
I'm not saying we should be cavalier about pushing current limits, but I also wouldn't be cavalier about doing things to hurt today's humans due to fears that are not well founded (because, again, negative population growth is now baked in to the world population pyramid, so that soon we won't be pushing the planet's limits any longer).
> soon we won't be pushing the planet's limits any longer
What constitutes as 'pushing limits' depends on the kind of planet that is considered tolerable. For many conservation-minded people, pushing the limits happened well before 7 billion.
A population shrinking to a quarter of it's size is only considered undesirable to some because the economy doesn't factor in the externalities of having a large population - e.g., climate change, reduced access to nature, increased stress, polluted environment, species loss, food chain collapse. The solution is to no longer permit these to be externalities, and I don't see that happening without government intervention on a global scale.
As for anyone concerned about an ageing population, within the next few decades human labor shortages will be solved with automation - to the point that there will be a shrinking job market. As for caring for the elderly, they will have access to new mobility technology, and life extension - at first expensive, but then trickling down to poorer people before 2 generations.
Indeed, when we lived in caves, there were only so many of them. We totally blew past the cave sustainability model thousands of years ago.
I'm not saying we should be cavalier about pushing current limits, but I also wouldn't be cavalier about doing things to hurt today's humans due to fears that are not well founded (because, again, negative population growth is now baked in to the world population pyramid, so that soon we won't be pushing the planet's limits any longer).