People...I’m an only child. I was raised by a single mother, with no siblings. This means there weren’t a whole heap of family members around, and none that were especially attractive. As a result of this, my views on incest have always been kind of skewed. I understand logically that we’re not meant to be attracted to relatives, but to be honest, I look at a lot of people with newfound respect for being able to make it through puberty with siblings that look like theirs.

Before we begin, let’s have a quick recap of how closely related we all actually are in the first place.

“In 1987, geneticists studied the mitochondrial DNA of 147 people of different races and found the DNA of all living people fall within one of two human lineages. One of these lineages descended solely from Africa, while the other contains traces of all other races. According to one geneticist, humans actually share more mitochondrial DNA than most primates. The mitochondrial DNA of two humans has only about half as many differences as the DNA of two other primates of the same species, suggesting that humans have a much more recent common ancestor than other primates. Geneticists have traced everyone’s DNA to a single woman, nicknamed Mitochondrial Eve, who probably lived around 200,000 years ago in Africa.

If you happen to have blue eyes, you and every other blue-eyed person on Earth share a single common ancestor who lived between 6,000 and 10,000 years ago. Before this common ancestor, every human being had brown eyes. Scientists aren’t sure why blue eyes spread so quickly around Europe, but theories have sprung up that blue eyes may be more useful in certain levels of daylight or were just considered sexually attractive to potential mates.

If you’re of European heritage, your lineage and the lineage of every European alive today can be traced to a set of ancestors that lived only 1,000 years ago, as researchers discovered after testing the DNA of over 2,000 people all across Europe. Researchers also found that, naturally, populations that lived closer together tended to be more related. Italians are slightly less related than other European populations, perhaps because they had a stable, independent population for many years, while people from the United Kingdom are more related to people from Ireland than people from other parts of the UK. Meanwhile, Eastern Europeans tend to be more related than the rest of Europe, which may be the result of the Slavic population boom that occurred about 1,000 years ago.”

Now obviously that’s a long way removed from how most of us view incest. We tend to imagine close blood relationships (parent-child and siblings) and most people’s instinctive reaction to incest is revulsion. Turns out there’s a good reason for that. Humans, like many animals, have evolved a “reverse sexual imprinting” process, also called the Westermarck effect. Basically if you grow up in the same house as someone else your brain kinda gets hardwired to see them as sexually repugnant. This is why so many people have issues discussing sex with or about their parents or siblings, because that sense of revulsion can overcompensate and go so far that you cease to see family members as sexual beings. To prove this theory, there was a study done on Israeli kibbutzim (like a socialist, Zionist farm). Kids on these kibbutzim were raised in communal groups based around age (but not around blood relation). They studied the marriage patterns of these kids later in life and found that out of the 3,000 marriages that occurred, only 14 were between children from the same peer group. And of those 14, not a single one had been raised together during the first 6 years of their life.

Here’s a story you might be familiar with. A king hears of a prophecy that his son will grow up to kill him. So he abandons his newborn son on a mountainside to be eaten by wolves. But some people who aren’t assholes discovered him and raised him as their own. Years later the boy meets the king on the road and after a fight about who had the right of way he kills the king. The boy continues into town, marries the newly widowed queen and becomes king (who says male privilege isn’t a thing). Later he finds out that the queen, his wife, is actually his mother. His mother kills herself and he gouges out both his eyes with a pin. Many years later an Austrian Neurologist will use this story as the basis for his theory - The Oedipus Complex. The myth is a perfect demonstration of what can happen without the Westermarck Effect. Oedipus wasn't raised with or by his parents and so had no innate revulsion towards them sexually.

Oedipus’ journey is actually one that many people will experience in their lifetime; blood relatives, separated at birth and reunited later only to experience sexual attraction, often unaware of their genetic relationship. This specific situation is referred to as Genetic Sexual Attraction or GSA. It’s an attraction between close relatives, (parents and children, siblings and half-siblings, or first and second cousins) who first meet when they’re adults. It’s important to note that they’re not raised with the person they end up in a relationship with. There is no risk of grooming or predation. Much of what concerns people about the concept incest is that it's inherently predatory, especially in the case of a parent-child relationship. Even with siblings there is the idea that one party could be manipulating the other or coercing them into a situation they’re not entirely comfortable with. GSA removes this power dynamic and places both parties on an even footing.

It’s not uncommon for siblings adopted out to different families to be reunited once they’re adults. Likewise, parents who were sperm donors, or who had to give their children up for adoption might be reunited later in life. In many instances, GSA occurs without either party realising they’re related at all.

So you’re on Tinder and you see some sexy mo-fo who kind of looks like someone you know. You go on a couple of dates and there’s definitely some chemistry there. You start boning, fall in love, and then...you find out you’re related. But how? Why? Well apparently we’re all just a little bit narcissistic and we’re naturally drawn to people that look like us. This is because we find people who resemble our face as more “trustworthy and cooperative". Hence, this happens a lot more frequently than you’d think. Don’t believe me? In Iceland there’s literally an app whose sole purpose is to stop you from unwittingly banging your family members.

In South Africa a couple who met in college and dated for five years only found out they were siblings once they were pregnant and preparing their wedding.

In a plot twist worthy of the Lannisters, a UK couple had their marriage annulled after they found out they were twins separated at birth.

All these people were in a situation where they unwittingly entered into an incestuous relationship and, upon realising it, wanted to GTFO. So what happens if you meet up with a long lost sibling or parent, aware of the relation? Surely then you’d be forewarned and forearmed against romantic attraction developing. Well, apparently not. Studies on GSA have placed the incidence of romantic emotions developing in these situations at 50%. And for many of these people the love and passion they experience is worth the social taboo and shunning they might experience as a result.

In 2007, in Germany, a sibling couple decided to challenge the laws around incest. They met as adults, got married and had children together, but under German law their marriage wasn’t valid. So they fought to have it recognised (they failed). In 2011, in the UK, a woman pregnant with her first child faced the fear of being court ordered to separate from the man she loved; her father. They had reunited as adults, and formed a relationship, but were concerned the publicity around the pregnancy would prompt the courts to react to their relationship.

The interesting anomaly with both of these couples is the inclusion of children. While the German couple had four children together, two of which had been diagnosed with unspecified disabilities, the UK couple insisted on getting an ultrasound at 3 months to determine if there were going to be any health effects for their child.

Many people who raise concerns about incestuous relationships do so under that familiar flag of “Won’t someone think of the children?!” And in this case, there is a strong argument against incest, since it increases the likelihood of developmental issues. So how valid are these concerns? Let’s start with a benchmark; how common are birth defects in the general population? Well in the U.S there’s a baby born with a birth defect every 4.5 minutes, so about 3% of births. That percentage increases though when you consider that not all defects are diagnosable at birth. If you expand the age range, then the percentage increases to 12-14% by school age. So how much does it go up by if, say, you had children with your cousin? A 2% increase in the likelihood of defects at birth. I know, it's a lot of maths.

To help put it into perspective; if your father was over 40 when you were conceived and you’re able bodied and neurotypical then you overcame some amazing odds. There’s a 1 in 5 chance of breast cancer in children with advanced paternal age. Children conceived by fathers over 40 have a 30% increased risk of epilepsy, a 37% increased risk of Down's syndrome, a 14% greater chance of childhood leukaemia, and a 70% increased likelihood of central nervous system cancers (such as brain tumours).

But wait, it gets better! If your dad was over 45, you have a threefold increased risk of retinoblastoma (a rare type of eye cancer), as well as an increased risk of autism and schizophrenia. Also achondroplasia, a common cause of dwarfism, is nearly eight times more prevalent in the children of fathers aged 50 and over.

So realistically you’re better off having kids with your cousin as long as both of you are under 40.

Don’t get too excited though, because if you’re looking to have kids with a parent or sibling then you’re probably going to want to hold off (if I had a dollar for every time I had to say that). A group of genetic counsellors reviewed research done on the outcomes of sex between direct relatives, specifically their kids.

“The researchers examined four studies (including the Czech research) on the effects of first degree incest on the health of the offspring. Forty percent of the children were born with either autosomal recessive disorders, congenital physical malformations, or severe intellectual deficits. And another 14 percent of them had mild mental disabilities. In short, the odds that a newborn child who is the product of brother-sister or father-daughter incest will suffer an early death, a severe birth defect or some mental deficiently approaches 50 percent.”

The moral of the story here is don’t have kids with your parents or siblings. However, there have been some interesting thought experiments raised about this very issue. If we look at eugenics as the practice of controlling who can breed with who on the basis of trying to eradicate certain negative outcomes, then isn’t outlawing marriage and sex between immediate relatives a form of eugenics? Aren’t we stripping people of their right to love and have children with whomever they wish under the guise of protecting not-yet-created children. And if that’s the case, shouldn’t we then be enforcing genetic screening for all couples hoping to procreate.

In 2010 a man named David Epstein was charged with third degree incest for allegedly having sex with his daughter. Let’s disregard whether or not Epstein was guilty, and whether or not you can have a consenting relationship with your own child, and focus instead on the law he was charged under. This law doesn’t just weigh in on “sexual intercourse” but also “oral sexual conduct or anal sexual conduct” meaning that regardless of whether or not you can get pregnant, it’s still illegal. Additionally it also applies to any close relative “whether through marriage or not” which means it’s not even distinguishing between genetic relatives and in-laws.

Let’s say that you meet up with a gorgeous stranger, fall in love and bond over your shared interests. You get married and only then realise the love of your life is actually your long lost sibling. Let’s also add that one or both of you got a vasectomy or tubal ligation, or perhaps you’re a same sex couple. At this point we have to acknowledge that no one was taken advantage of or groomed into the relationship since you only met as adults, and there’s no risk to any future offspring. As a society, are we still revolted and repulsed or can we acknowledge that at this point it’s purely about a constructed taboo.

Sue Cowling is the deputy director of the Post Adoption Centre raises valid concerns about what this taboo means for research into issues such as GSA and the people likely to be impacted by it.

“Because of the revulsion aroused by incest, and the stigma attached to anyone who admits experiencing GSA...the condition remains obscured by myth, tainted by smutty innuendo, under-reported by sufferers and, worse, virtually ignored in academic circles. Although, occasionally, a story involving GSA is given predictably lurid tabloid coverage, ignorance prevails.

The lack of any serious scientific research is especially disturbing in view of the growing number of reunions between adoptees and their birth parents, and the prospect of many future reunions between children born through IVF involving sperm and egg donors. In the view of Sue Cowling, deputy director of the Post-Adoption Centre, "Genetic sexual attraction associated with IVF births is a time bomb waiting to go off." Cowling, like many professionals, suspects the subject has remained a no-go area, even for psychologists, because even in a society wide awake to the spectre of paedophilia and sexual abuse in families, GSA - which falls into neither category - threatens to explode too many cosy assumptions about "normal" and aberrant sexual instincts.”

So maybe it’s time for us to put away our instinctive revulsion and vomit emojis and actually start discussing incest and the fact that it doesn’t always look the way we expect it to. That like so many things related to sex it deserves far more research and interest than we’re currently giving it.

Incest isn’t just a trending porn genre and favourite fan fiction trope, it’s a real thing that impacts real people’s lives and relationships. We need to start thinking about it critically so that we can adjust our legislation and our attitudes accordingly. Sticking our fingers in our ears and chanting “la la la too gross” isn’t helpful to anyone. So let’s suck it up and start talking about incest like adults.

That is all.

You may go now.

Sexual Sins: Incest