Alternative economic models might exist in nature. There are many different types of cooperative systems in the natural world. I propose that capitalism is an attempt to create a natural like system of economics. However it was created when the idea of "Nature, red in tooth and claw" was the common representation of evolution as decent through natural selection. In reality, many of the systems that have grown to become self-perpetuating rely on some form of natural cooperation between or within species.
We all think we are better adapted than squirrels to exist on this planet right. We have larger brains, we have mastered technology that the squirrel world might never be able to utilize (though it is fun to imagine squirrels making use of trenching equipment and GPS technology to bury and keep track of their nuts). But when it comes to economics, they beat us hands down. Considering their short life, they bury thousands of seeds and nuts, it is estimated that a full third of these will never be found. These abandoned hordes germinate and generations later, supply food for the great-great-great-grand-squirrel of the planter.
They contribute a third of their labor towards forest management! They are actively creating conditions to ensure the success of their species well into the future. This is most likely not the direct result of a big squirrel meeting, where they mandated a percentage of "lost nuts", but squirrels have not adapted the organizational trait that characterizes humans. Yet despite our "advanced" adaptation, we are still collectively unable to match or trump this level of sustainability.
Ant and bee populations also present another possible natural economic system. Here we have social stratification; workers, warriors, queens and her drones, all with specific job descriptions and traits to match. There is considerable evidence that they even have basic intra-collective communication skills. Decisions made by individuals tend to lopsidedly favor the collective welfare of the hive or nest. This often translates to inter-generational success and empire expansion. But at the cost of individuality and the personal freedom.
Despite the success of the hive model, it is somewhat antithetical to apply to humans. Unfortunately for vertically integrated models (corporate type), we do not preform our best when we act exclusively through directives from the top (micro-management). Ants however do not receive "orders" per-say, they have intrinsic behaviors that are triggered by the actions of others. That is to say, they act autonomously, but with the single interests of the collective as their highest priority. If only business could generate this single-mindedness with in its ranks. (They probably could if they would forget about cost benefit analysis when it came to how they treat their employees, but that is a different story.)
Both of these models do have (imperfect) parallels in human behavior. The squirrel is like the bottom up approach to sustainability. Creating resilient sustainable communities from personal involvement; programs like the capital hill food forest in Seattle is an example of this. The other model is top down management, Japan's highly successful forestry management program through careful accounting and enforcement. One thing both of these models share that capitalism in general is completely ignorant too, is sustainability over profit.
For the squirrel, the energy it spends to amass the surplus could easily be spent on much more personal gains, expanding territory and harem for example. For the ant colony, if the interests of individuals were to become more important that the collective good, the nest would surely collapse in decay within only a few generations. The take-away is basically, individualism be it bottom up or top down, is somewhat at odds with sustainability.