Most of us know that incest is wrong, either through cultural conditioning or what appear to be innate evolutionary cues, yet some humans can’t seem to resist the urge to have sex with their relatives. In fact, since the DNA of every living human is 99.9 percent the same, it may be much more common than we think. Still, that doesn’t mean incest can be acceptable in any case. As we will see, breeding with a close relative can result in some dire consequences.
For most of us, the idea of falling hopelessly in love with a close relative is probably both disgusting and inconceivable, but for up to 50 percent of people who reunite with their siblings, parents, or offspring after separating at birth, developing obsessive feelings for a family member is a reality. These strange emotions are the result of a condition known as genetic sexual attraction (GSA), and it has reportedly become so common that post-adoption agencies warn their clients about it and provide specific training to their counselors to treat it.
Unfortunately, not much is known about GSA because most people are afraid to admit that they’re attracted to a close relative and the subject of incest is still very taboo among academics and psychologists, resulting in a lack of research on the subject. What is known is that the attraction doesn’t always lead to sex. Sometimes, it’s just an overwhelming desire to be around and touch the long-lost relative. When it does result in a sexual relationship, it’s usually between reunited brothers and sisters. One psychiatrist , who conducted one of the only known studies on the condition, cautions that there is a stark difference between traditional incest and GSA. While GSA sufferers are technically committing acts of incest, they are repulsed by the thought of having sex with family members they grew up with.
What could cause something like this to happen? According to Freud, we’re all repressing incestuous urges, and recent studies suggest that the good doctor may have been at least somewhat right. In 2010, researchers found that people tended to partner with those who resembled their opposite sex parent. Specifically, scientists found that women were attracted to men whose features resembled the central portions of their father’s faces, while men were attracted to women who shared similarities with the lower parts of their mother’s faces. An earlier study also found that men and women, respectively, opted for partners who had the same eye and hair color of their opposite sex parent, while yet another study found that children of older parents gravitated toward older partners.
The theory is that we are “imprinted” from a young age to seek out the familiar by mating with people who resemble those who raised us. According to psychologists, when you see a face that is similar to yours, you tend to believe the person it belongs to is more trustworthy and cooperative. One Scottish study found that women were most attracted to men who were essentially masculine versions of themselves. Psychologists believe that this is because overt masculinity can sometimes make women wary, and familiar facial features may help to build trust.
Though it might seem counter-intuitive, given all the issues with inbreeding, evolutionary theory says that we’re attracted to mates who resemble our parents because doing so may promote our own genes. To make sure we don’t choose partners with genes that are too similar, though, humans subconsciously employ guides such as scent to attract us towards those with sufficient genetic diversity.