(07-18-2013, 04:53 PM)Callipygian Wrote: Allow me to offer the biological perspective on in-breeding. Fair warning, this next paragraph will contain a bit of science and a little math. Skip to the paragraph after if you don't understand it.
Consanguinity (relationship through a common ancestor) is the term biologists use to describe this sort of relationship, and historically, consanguineous relationships have gotten a bad rap. From the mathematical point of view of population genetics, however, they become a lot more transparent. In-breeding within a population leads to a very peculiar effect. Genetic diseases tend to appear as rare recessive traits that only surface when an individual acquires two copies of the recessive gene. In an in-breeding population, this tends to occur more often due to the shared ancestry, but the opposite occurs more often as well. You also get more individuals carrying both of the dominant genes. I've done the math before in my college bio-statistics class, and it was a sound conclusion. You end up breeding out the carriers (individuals that have one copy of the disease gene, which is how it survives in the gene-pool). I've seen it theorized that each individual of an out-breeding population carries an average of seven deadly recessive traits, which is why in-breeding appears to be so bad. Over time, however, an in-breeding population will weed out those traits faster, depending on how closely related the consanguineous relationships are.
To sum up what the above means metaphorically. When it comes to in-breeding, in the short term, you get a lot of bad eggs, but your likelihood of getting a really good egg (twice the size with double yolks or something) is also higher. Over time, you obviously weed out the individuals with lower fitness (the slow ones with the terrible teeth and hemophilia), but you also remove the carriers, the ones where these genetic diseases hide within the population. For the first ten to twenty generations, the population on average suffers, but after that, they tend to be better off in terms of fitness than a continually out-breeding population, and your likelihood of producing one individual with exceptional fitness is actually higher than an out-breeding population.
Now if you consider the fact that in the Miqo'te structure, where it's basically a lottery and a winning male wins big, I'd actually say that in-breeding is not that frowned upon. Using the egg analogy from before, if that one special egg out of the dozen happens to be male, he's guaranteed to become a breeder when he reaches maturity, which from the point of view of fitness is a massive success and potentially worth the risk. There are species on earth (like the Japanese quail) in which the preferred mate is a first cousin for this reason. Over time, in-breeding breeds out the bad genes much faster than out-breeding.
To give a real-life human example, consider the royal families of Europe. They practiced a mild form of in-breeding, seeing as how they all inter-married over centuries, while at the same time out-lawing in-breeding among the populace. Why did that happen? The prevailing theory is one of wealth distribution. If the highest royals are forced to outbreed, it spreads their wealth around, as they are continually forced to choose a spouse less privileged than themselves. In-breeding at the highest tier of society guarantees that their spouse will bring in a comparable amount of wealth and aid in consolidating power. Conversely, if the lesser nobility are allowed to do the same, they could potentially maintain and amass enough wealth to become a threat to the throne. Forcing them to outbreed spreads the wealth around and maintains a lower average wealth and influence compared to the royals. In addition to a long-term biological benefit, there's also a short-term socioeconomic benefit to offset the short-term genetic cost.
TL;DR: In-breeding is not as bad as everyone has been led to believe. In the long-term, it actually improves the genetic fitness of a population. Socio-economic factors in human society offset the short-term costs.
I admit I like how you put it all into perspective.
