Blood Calls For Blood

Well, not really. But kinda. Allow me to explain.

Okay, for some reason my posts have been sort of turning into me dumping all my thoughts on a particular matter together, even if it is a collection of links and explanations. I guess it's because it helps me clarify things in my own mind. Nevertheless, we continue.

Now, anyone who has read a "trashy romance novel", watched a soap opera, the odd crime drama, or picked up a mythology book knows that siblings or other relatives "hooking up" is no rare thing in fiction. However, none of these things tend to go into the psychology of it - or at least explaining that there is psychology behind it. I'm going to spend this post explaining that there are in fact theories behind this behaviour and siting examples to prove my point. I've actually found works of fiction that work this into the story in an interesting way because the author actually understands the psychology behind it.

The first effect is called Genetic Sexual Attraction, which is exactly what it says on the tin - attraction to those one is genetically related to... who they first meet as adults. Often this happens as the result of adoption, infidelity, etc - basically circumstances that stop the siblings/relatives from meeting before adulthood or, in many cases, even knowing of their relationship.

There are a couple of theories behind why this happens. Surveys find that people commonly find that faces similar to their own are more attractive - usally such things are hereditary. In 2004 Bereczkei argued that children "imprint" on the opposite sex parent and hence go after people with similar interests and personality traits. However there is a great deal of debate over this as we don't know if such traits are inheritable and to what extent. Anyway, if inheritable they will likely stick to close relatives.
Truth be told, I'm very divided on that particular issue (whether or not personalities/interests are inheritable) and am likely to go into detail in another post.

Now, you're probably wondering what I meant by "imprinting" and if you've read/watched Twilight you will recognize it from Breaking Dawn (whether or not you are smiling or cringing at the reference is subjective), however the term "describe[s] situations in which an animal or person learns the characteristics of some stimulus". The most common version is filial imprinting where the child!animal takes on the characteristics/behaviours of the parent!animal. Such situations include those were an animal of one species spends it's "childhood" with animals of another so it grows to act like them - for instance I owned a cat which thought it was a dog. Next type is sexual imprinting, which is where child!animals learn to be attracted to traits that the animals that raised them possess - a contributor to Bereczkei's theory.

Finally we take on the other side of this argument - the Westermarck Effect. This is reverse sexual imprinting, and why children don't normally feel sexual attraction to siblings, parents, and other close relatives. It works on the basis that where two people who live in close proximinity during the first few years of life they will become sexually desensitized to each other. This has been observed in many situations, such as the Israeli kibbutzim, such that basically where children are raised in groups there is a very small number of marriages between members of that group in the long run. In the mentioned example, of nearly 3,000 marriages only 14 happened in the same group, and none of them were raised together during the first 6 years of life. Therefore children who are raised together in the first 6 years of life are unlikely to become sexually attracted to each other at a later point.

What I like about these theories combined is that they debunk other theories... like Freud's (dude, not everything comes down to sex). While Freud argued that all children lust after family members based on his having an "erotic reaction" on seeing his mother dress, Westermarck pointed out that Freud was raised by a wetnurse and thus never desensitized to her.

Anyway, many historical accounts of this can be seen. In ancient Egypt, in order to preserve the royal blood (which was carried through the women) royalty used to raise boys and girls separately before marrying the next Pharoah to his (half)sister - since they never met in the first 6 years, the Westermarck effect was avoided. However in Europe at some point they attemped the same thing only to have the King and Queen refuse to breed because they saw each other as brother and sister due to being raised together.
This is also why marriages between cousins were so much more popular as a combined affect of both effects - not being raised together during the critical phase and being genetically similar enough to cause GSA.

For the sake of fairness I will mention that the genetic side-effects of inbreeding between cousins have been mostly exaggerated the likelihood of birth defects is only 4% compared to the usual 2%. However, as you can see in the British royal family Haemophilia has been concentrated due to a long history of inbreeding.

Actually, Fridge Brilliance in that the Greek Pantheon's notorious inbreeding actually makes sense since none of them were raised together, since of the first six gods Hestia, Demeter, Hera, Hades, Poseidon, and Zeus all but the youngest were devoured by Chronos and Zeus was raised by nympths on Crete. Therefore none of them were technically raised together so it would be natural for Zeus to be attracted to his sisters (having married Hera, having Persephone with Demeter, and Hestia was apparently so desired that she pledged herself to chastity). Depending on the "being eaten by Daddy" situation, Poseidon's attraction to Demeter may or may not be justified, but Hades's attraction to Persephone would certainly fall under here due to this effect since nobody ever visited him (as well as the fact that he lived a dull existence and she was just the perfect ray of sunshine).

What, ironically, makes less sense is the Egyptian Pantheon unless their gods were raised the same way as their royalty - I haven't read anything to specify so.

Anyway, hopefully this has proved enlightening in some way or at least gave you something weird to think about... which, let's face it, is clearly my main intention.