Islands in the Sky
After following a few discussions in the Mars One-Aspiring Martians Group on Facebook, I began thinking about the minimum human requirements for starting a viable independent colony on another planet (or in space for that matter). Any colony that is incapable of being independent of the Earthbound civilization (or even organization) that spawned it is (under the best of circumstances) doomed to share it's progenitor's fate. In that event, any colonists who have no transportation back to Earth will certainly die.
Anthropologist John Moore speculates that a number around 160 people will be necessary to have a biologically viable space colony. It isn't clear to me that such a number will be able to maintain the life-sustaining technologies necessary to keep the space colony going. If we create a colony that is dependent on computer technology to maintain it, how will the colonists be able to engineer computer replacement parts after they fail? Also, how will the colonists be able to advance their technology base over time? How will they teach their progeny to replace the preceding generation of technologists? You might need between two and five thousand people (a small town's population) or perhaps more to maintain an independently viable technological civilization in a colony.
The picture at the head of this article is a starry background sprinkled with images of some of the world's smallest inhabited islands: The Pitcairn's Islands have a population of just 50 people. Foula, an isolated British Shetland Island, has a population of just 38. Nauru has a population of 9,300. Rapa Nui (Easter Island) has a population of 5,700. Anuta has a population of 300. These tiny islands are much like space colonies, but at least they have the distinct advantage that they exist in relatively benign environments and in relatively close proximity to outside supplies. This will most certainly not be the case for distant space colonies.