Is Cousin Marriage Really All That Bad?

Oh, this is going to be a fun one – I can see some of you squirming in your seats already! And that's the thing, isn't it? Cousin marriages are a bit icky, a thing to be mocked or pitied, in Western culture at least. You might wonder why we even need to explore this topic, I mean, it's just a bit gross, yeah? Who'd ever want to marry their cousin? Unless they live in a trailer park, amirite? Well, I grew up in a place where those sorts of jokes were common, so maybe I'm the right person to break this one down. Let's begin by looking at the legal situation.

Where I live, in England, it is legal for two first cousins to marry. That's the closest relative you're allowed to wed under English law. This practice predates any of the formal laws regarding marriage in the UK. The earliest record of its acceptance is in the 1560 Church of England list of forbidden marriages. It contains a long list of those relatives that one may not marry – and cousins are not mentioned at all. The Marriage Act of 1907 kept things as they were, in respect of cousins getting hitched, as did the three subsequent updated Marriage Acts of the 20th Century. Looks like the Church and State are well on board with cousin-nookie here in Blighty!

So what was the context for the original law, and the following updates that kept it legal? When the rules were first laid down, cousin-marriages would have been most common among members of the aristocracy. These unions would have been a means of retaining property, titles & status, and “strengthening” the bloodline. Keeping it in the family, so to speak. Conversely, the very poorest in British society also had a tradition of cousins marrying – because it allowed the family to save money – only one set of guests to invite if bride and groom are from the same family! There was also the matter of not needing to pay a dowry, although that one has definitely died out in White British culture. Cousin-marriage remained common among certain social groups up until the end of the 19th Century in Europe – which was around the time we started to get a good understanding of genetics. The fear of creating deformed and sick children came in to the public consciousness, and the practice slipped into obsolescence. But it remained on the statute, and it's still 100% legal to this day.

These days, cousin-marriage among indigenous Brits is seen as a bit of an oddity, confined to isolated communities with an “inbred” stereotype. As I mentioned, I grew up in one of these dodgy backwaters, and I'm aware of two (happy) cousin-marriages. It's more of a notable issue that I have a relative with polydactyly, although this more often occurs spontaneously than through heredity (yes, I have also heard all the jokes about webbed feet). It seems that the fear and stigma of the turn of the last century have had a lingering effect on the acceptability of kissing cousins.

The situation is further complicated by a recent change in the make-up of the UK population. Around 1900, early geneticists (and eugenicists, let's be honest) could see (for example) the stark problem of haemophilia in the Royal families of Europe. They were well into getting jiggy with their close relatives – and look where that got them! But... there is more to it than the simple matter of cousins getting it on together. There have been a handful (relatively speaking) of first-cousin-marriages between White Brits since 1900, and there's not been much to report. Some have had kids, some haven't, and they have all the same joys and problems that you'd expect within any other family. Some of the children have health problems and some don't – also similar to most families. We've got better at identifying & treating health problems in babies, so a lot more gets picked up these days. So, there's not much to talk about in that respect. But the conversation has shifted focus.

The UK presently has about 1.5% of its population made up by people of Pakistani origin, who have a stronger and enduring tradition of cousin-marriage. The initial reaction is to jump to the conclusion that this is a remnant of a backwards culture, hopefully to be assimilated. They probably have a ton of deformed babies due to all that inbreeding, yeah? Hold your horses. We need to look at what the evidence says.

An interesting, yet tragic, example is the manifestation of a condition known as “Polygamous Down's” among fundamentalist Mormons in Utah. The condition has nothing to do with actual Down's Syndrome, but it appears to have been given this name due to the distinctive facial characteristics of those who have it. It's a horrible illness, causing profound mental and physical disabilities. It's caused by an inherited problem in producing fumarase, an enzyme responsible for transferring energy to cells. Without this enzyme, the body and brain cannot grow & develop properly. Fortunately, it's extremely rare – with odds of about 400 million to one of a child inheriting it – except in Utah. Within the Fundamentalist Mormon community, the odds skyrocket to about one in 400. So what's going on? Well, the clue is in the question – it's due to the marriage practices of the community. Polygamy itself isn't to blame, but polygamy within a closed community is. People within the fundamentalist Mormon community are almost certain to be closely related to their spouse – because the practice of taking many wives reduces the number of men able to share their genes. Further narrowing the genetic diversity is the reluctance to marry outside of the community, leading to a lack of potential spouses to whom one is not related. What this results in is an isolated group of humans that become more closely-related with each generation, increasing the probability of genetic mutations (not all mutations are bad; it's a fundamental component of new species evolving – but this one is really, really bad). So the problem here isn't of relatives marrying, but of marriage only between relatives – this is the same issue that drove the prevalence of haemophilia in the European Royal Families.

Let's return to the example of British Pakistani families. While cousin-marriage has gone out of fashion among the White British population, these relative newcomers view it more favourably. This has prompted discussions of the morality and risks of first-cousin-marriage, including from those who should really know better. MPs Ann Cryer and Phil Woollas expressed their concern about the risk of genetic defects in children born to these families:

"They are in denial... The price to pay is often in either babies being born dead, babies being born very early and babies being born with very severe genetically-transmitted disorders." - MP for Keighley, Ann Cryer.

"A lot of arranged marriages are with first cousins, and that produces lots of genetic problems in terms of disability [in children]," - Phil Woollas, who was later to become Immigration Secretary.

However, these “common-sense” statements don't make as much sense as they seem to at face value. Firstly, the question being asked here is tied in with assumptions about race and cultural integration, and a wrong foot can blow up all sorts of tensions and prejudices. Neither of these statements has been worded particularly sensitively. Cultural leftovers from the early 1900s combine a fear of cousin-marriage with the everyday racism of the early 2000s.

So then, is there any merit to the argument scientifically speaking? A study conducted at Leeds University observed the outcome of 11,396 births in Bradford between 2007 and 2011. It may sound alarming and predictable to hear that birth defects, in children born to first cousins, occurred at double the rate of unrelated parents, but steady your confirmation bias. First off, we need to understand what is meant by a “birth defect”. This could be anything from barely perceptible cosmetic problems (like a funny shaped ear, or heterochromia), right up to serious and life-threatening conditions (e.g. anencephaly or Down's syndrome). Most birth defects are less severe and treatable, and many are invisible and go undetected until adulthood – you might have one and be unaware of it. I discovered in my early 30s that I have a bicornuate uterus; a chance discovery made when the sonographer was looking for something else.

The actual rate of birth defects in the general population is about 3%, with those children of cousin-marriages having an occurrence of 6%. So there is still a 94% probability that parents who are cousins will have a completely unaffected child. For the unlucky 6%, there are treatments available and most of their problems can be overcome. They will still be as loved and wanted as if they had been born into “ordinary” families.

Before we discuss family dynamics any further, there is something more to be said on the prevalence of birth defects. In the UK, maternal age is on the increase, and yet we are remarkably silent about the 6% risk that a White British woman aged over 35 has of giving birth to a baby with a defect. Think of it like this: how many older parents do you know, how many of them have “deformed” offspring, and how many love their children no matter what medical issue exists? Funny, isn't it, how we don't make these judgements about families in our own communities? But those foreigners, coming over here, talking all funny and marrying their cousins, they're the problem. Apparently.

There have been a few stories in the British media recently, presumably with the aim of increasing understanding and integration, of couples that are first cousins. It's not all positive, there are accounts of families that have experienced a spate of serious birth defects, and there are families that repeat cousin marriage from generation to generation, potentially consolidating genetic defects that could appear anywhere down the family line. And there are some which help to explain why cousin marriage is a popular activity in the British Pakistani community – the shared values of both parties in a world that cherishes different ideals, for one.

The whole truth is that it's a far more complicated issue than a sensationalist headline or political soundbite can do justice to. Cousin-marriage is on the rise in Britain, but it's hardly at epidemic levels. A cultural and demographic shift in some regions has led to increases in the practice, and we don't know if that trend will continue. The scientific evidence shows a slightly higher incidence of birth defects in children born to first cousins, but viewed alongside other risk factors, it's not significant. Other cultures value the practice, yet in the West we find it barely acceptable. Perhaps that is the biggest problem with cousin-marriage: that we are so absorbed in our own prejudices that we don't pay attention to the facts, or care for the truth. Like so many other moral matters, perhaps the solution to our cultural dislike of cousin-marriage is simply to not marry one's own cousin?