Someday, either because of curiosity, necessity, or both, the human species will need to leave planet Earth and travel to the stars. But we must consider several important factors before we begin our journey. For example, how fast can we get to the planets we want to colonize, and how many people will we need to put on starships to make that happen? Although a previous study in 2002 stated that only 150 people would be needed, a new study by John Moore at the University of Florida estimates that the number is closer to 10,000, or even possibly 40,000 will be necessary.
So why so many people? The first thing to look at is that even the nearest star system, Proxima Centauri, is over four light-years away from Earth. At our current technology level, it would take us thousands of years to get there. This means we’d need to have a starship where generations are born and then die without ever seeing the planet that will eventually be colonized, not to mention the planet that they came from. 150 people could probably handle that, but there would be very little genetic diversity, which could increase susceptibility to genetic diseases. In Moore’s study, a larger number — at least 10,000 people — would ensure viable diversity in the human gene pool.
The second reason we need so many people for space colonization is that we must take into account that catastrophes will happen. There will be illnesses, mechanical failures, alien slave raids, and other unseen events that could drastically reduce the population of space colonists. With a larger number of people spread out over multiple spaceships, these occurrences won’t have the potential to be catastrophic.
So how did Moore come up with these numbers? He used a computer model built with William Gardner-O’Kearney, an archaeologist at Portland State. The model’s algorithm worked out different events that might happen during space travel. Using a starting population size over a course of 300 years (30 generations), the algorithm ran 10 times for each number with the result being the average of each simulation’s final count. This accounts for random things that might happen in space that will affect the population. The results showed that starting with 40,000 people keeps genetic diversity at 100 percent, but that even with just 10,000 people, diversity remains workable. In the case of events that might affect the population count, both numbers survive such occurrences well, leaving enough colonists to maintain genetic diversity. Anything less than 10,000, though, and the viability drops significantly.
Of course, if we'd just bother to invent Star Trek’s warp drive, this would all be moot. So let's get on that, shall we?