Animals, humans included, are not naturally sustainable using the common definition of the term. They/we will tend to consume resources and grow, until something (usually starvation or disease) curbs the growth and resets the system. No human system has avoided this boom/bust cycle, including the communities in Africa/Asia that were previously mentioned in the thread. In fact, there is evidence that both the Gobi and Saharan deserts were caused by the actions of those early cultures.
One problem with attempting to be sustainable, using the common definition, is a failure to calculate all of the costs. One big one is that modern economic systems are dependent upon growth. Another is a failure to calculate all of the costs associated with some choice. The one that is commonly referenced is the use of reusable mugs versus paper cups for coffee. These numbers are from memory and may be a little off, but it takes about three years of reuse (and that means just using one cup per person) to break even on the impact of using paper cups. For a ceramic mug the numbers are even worse, about 8 years to break even. How many people end up using one single cup for that long? So the paper cups are usually more environmentally sustainable--something contrary to the accepted belief. Further the paper cups provide a much higher economic boost to the community.
Like Roody said above the key to any community is making things have a good economic basis. Recycling is really just starting to make such sense. For much of my life, these recycling programs cost money. Now they are starting to break even. In the US long range plans typically do include an economic component; however, since economics is more art than science, it doesn't take much political pressure to change the numbers to something the politicians want them to say. The proverbial rose colored glasses.
Personally, I have faith in technology and human invention. By and large our communities are cleaner, healthier than they have ever been in the course of human history (1st world). Non-essential concerns such as sustainability are the product of economic prosperity. That prosperity yields the ability to improve living conditions. Maintaining that prosperity is the key to any hopes for sustainability.