I'd like to quote a line from the matrix that I found very interesting.
Every mammal on this planet instinctively develops a natural equilibrium with the surrounding environment. But you humans do not. You move to an area and you multiply and multiply until every natural resource is consumed and the only way you can survive is to spread to another area. There is another organism on this planet that follows the same pattern. Do you know what that is? A virus.
A friend of mine says that other mammals dont find equilibrium on their own. they find it through being eaten by predators. usually its their young who are eaten, as the old become smart. sound familiar?