Caution: The following post started on topic, but quickly spun off on a tangent until it ended in personal musing. As such it really has nothing to do with the subject at hand and can be skipped.
Following the earlier point, everything needs to find an equilibrium or it will spin into chaos. This is true in all science and everywhere in life. If there is nothing to check human growth, humans will continue to expand. A similar analogy would be to look at our sun. There is nothing to keep this star in check, and so, billions of years in the future, it will overwhelm our world. Similarly we will continue to overwhelm everything. Everything works to either escape the system or reach an equilibrium and even our moon is steadily spinning ever away from us until it will one day reach an equilibrium where its orbit around the earth is equal to the earths rotation (at this time the earth will rotate about forty times slower and the moon will stay on one side of the planet at all times). In this particular story, and in the following discussion, it's humans that keep each other in check, but in recent times, we have in a way stopped keeping each other in check. There are no wars, there is no murder, and we can cure plagues, so we must hope that we can either stop our own growth and find an equilibrium, escape the limits of our system, or have an equilibrium made for us, probably self extinction or the collapse of civilization. This has happened time and time again as civilizations collapsed such as the dynasities of china, the roman empire, Great Brittain (yes fragments of that empire still live on, but they don't encompass nearly as much as they used to). I worry sometimes that if our civilization (now world wide) collapses again under the strain of our own weight, there will be no recovery, not for thousands of years. And sometimes... sometimes I wonder if this has ever happened before.