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Imagine humans were to colonize a distant planet and it was a single one-way trip. How many people would they need to bring?

Obviously 2 is the minimum, but that would result in a lot of inbreeding.

So what number is the minimum number of people you can have in an isolated community and still maintain a healthy diversity?

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Without doing any digging, my understanding is that first cousins can really interbreed without too much risk. So a first estimate that 2 completely unrelated mating pairs from distant parts of the human genetic tree might make a minimal gene pool candidate. I can see an argument being made for 8 too. – shigeta Dec 18 '12 at 2:08

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Actually it is a very important question for laboratory animals (and, I imagine, endangered species) and was calculated to be 25 couples.

With any number of animals (including humans), there is always some inbreeding happening, but you can reduce it with the number of breeding pairs and careful pairing. When you get to 25 pairs (50 animals) and have complete control over pairing, you can sustain the genetic diversity practically infinitely (especially if you take into account spontaneous mutations).

Of course, such control over who can have children with who (plus whether one is at all allowed to procreate and what will be the sex of their children!) would be questionable morally, so in case of populating a distant planet, we would need a larger group, to provide for sexual preferences, fertility problems etc.

Some information on laboratory outbred stocks.

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nice answer - it makes me realize though that there are problems keeping some dog breeds viable - they tend to accumulate too many diseases (link below). Yet there must be thousands of animals in most breeds that are in trouble. Is this because controlled breeding is used differently (emphasizing breeding traits vs diversity), because there was few original dogs in the pool, or why? nytimes.com/2011/11/27/magazine/… – shigeta Dec 18 '12 at 18:59
I am no expert on dogs, but did learn a bit about in- and outreeding. Each dog breed is either open or closed. In a closed breed, only offspring of animals already belonging to this race belong to the race. In an open breed any animal that looks similar enough (or has other important traits, characteristic for the breed) can be a parent of a "breed" litter. Under certain circumstances (e.g. too few animals in the breed, too bad overall health of the breed) a closed breed can be opened and after the problem is solved, closed again. – jkadlubowska Dec 19 '12 at 9:34

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