How Many People Do You Need To Colonize The Next Star System – 150 or 40,000?
THIS is an interesting little calculation that’s been made about how many people you would need on your spaceship if you were to set off and try to colonise the next star system over. Well, OK, it’s interesting to me as someone who imbibed so much SF and Fantasy stuff when in my long ago youth at least. And the answer is a very much larger number of people than you might think.
Here’s what the problem is:
Entire generations of people would be born, live, and die before the ship reached its destination. This brings up the question of how many people you need to send on a hypothetical interstellar mission to sustain sufficient genetic diversity. And a new study sets the bar much higher than Moore’s 150 people.
According to Portland State University anthropologist Cameron Smith, any such starship would have to carry a minimum of 10,000 people to secure the success of the endeavor. And a starting population of 40,000 would be even better, in case a large percentage of the population died during during the journey.
To get that low number you simply calculate how many people you need to have alive at the end of the trip, assume they’ll have lots of kids and then they manage to get on with things. However, humans don’t really work that way. Over centuries such a small group would become horribly inbred. OK, you can take account of that by making sure of your breeding plans before everyone goes off. But that’s still not enough. Because there’s enormous variation in the human genome and taking only 150 people will mean that you’re not taking enough of that variation. And what you do take will also find much of it being lost down the generations. In order to be able to keep people as people, in all their near infinite variation, you need to take a number in the 10 to 40 thousand range. Which is the rather surprising conclusion of this research.
We might note that the various emigrations of people on Earth were never this large: no one thinks that there were 40,000 Aborigines arriving in Oz at the same time, or Polynesians in Hawaii: but these migrations were rather different. Because they were not single events, there were waves of people, the later arrivals being able to make up for that lack of genetic diversity in the original groups.But it does show that we’ve got something of a problem with this populating the universe idea: it’s not just building a ship that will last for a thousand years or two, it’s building one that can take 10,000 people or more.