Dominic Wilkinson, University of Oxford
A bill that proposes to ban first-cousin marriage in the UK will receive its second reading in the House of Commons on March 7.
The bill, proposed by Conservative former minister Richard Holden, follows the introduction of a ban on cousin marriages that came into effect in Norway in 2023 and a planned ban in Sweden from mid-2026.
Different reasons might be given for proposing to ban first-cousin marriage. However, one significant reason given by supporters of these bans is concern for public health. Holden claimed in his speech to parliament that: “First-cousin marriage should be banned on the basis of health risk alone.”
In the UK, a long-standing research study of childhood outcomes in Bradford, where there has traditionally been a high rate of cousin marriages within the Pakistani community, recently found that children of first cousin parents had higher rates of learning and speech problems and more visits to hospitals and doctors.
The increased incidence of certain genetic illnesses in children of related parents has long been recognised. When parents are closely related, they are more likely to carry the same faulty genes.
If both parents pass on the same faulty gene to their child, the child has a higher chance of developing a genetic illness (about double the risk of parents who aren’t related). The Bradford study had earlier found that first-cousin marriages were linked to 30% of cases of birth defects in the studied population.
The recent study suggests that even once you exclude those children diagnosed with recessive genetic conditions – and even after adjusting for other risk factors such as poverty – the children had higher rates of illness and developmental problems.
Although it is laudable to wish to seek measures to prevent health and learning problems in future children, there is a fundamental ethical challenge.
Banning first-cousin marriage will not prevent children from having genetic illness or health problems, rather, it will prevent some children from being born and mean that different children (with a lower chance of genetic or other problems) are born instead.
Harm principle
A basic legal and ethical principle, defended by the 19th-century philosopher John Stuart Mill, is that states are only justified in restricting the basic freedoms of individuals to prevent harm to others. But if we take the “harm principle” seriously, then the health case for a marriage ban dissolves. There will be no child who is saved from illness or harm because of a law banning first-cousin marriage.
It might be thought that a ban would still be justified, based on community health rather than for the sake of specific children. The idea would be that it would be important to prevent first-cousin marriage because of the high rate of genetic illness in offspring. Perhaps the hope would be to reduce pressure on the health system. But there are several problems with this argument.
First, most children of parents who are first cousins are healthy. The rate of genetic or congenital problems is 6% (compared with 3% in parents who are not related). This means that 94% of children will not have genetic or congenital problems. Or to put it another way, given the small additional risk, over 30 couples would have to be prevented from marrying to prevent one child from being born with an inherited genetic problem. The same argument applies to the extra learning problems seen in the Bradford study that were not diagnosed as genetic problems: most children of first-cousin parents did not have learning difficulties or serious illness.
Next, a ban on cousin marriage to reduce the rates of illness or learning problems in their offspring would represent an attempt to prevent certain people from having children for the sake of benefiting the population. But once we frame it in that way, it is clear that such an effort would be eugenic, based on a particular group’s perceived genetic fitness to reproduce.
Such a policy would be an example of some of the most troubling forms of eugenics: restricting basic freedoms (the freedom to marry and have children) for the sake of the common good.
Third, the health-based reason to ban first-cousin marriages is because of the elevated rate of birth defects and health problems in children. However, the rate of these problems is also increased in parents who are related more distantly. And in close-knit ethnic groups there can be shared genes and increased rate of congenital problems (so-called endogamy), even without cousin marriage.
If we ban first-cousin marriages, families could shift to others within their extended family. Or, if we wanted to prevent higher rates of birth defects, we might need to ban not just first- and second-cousin marriages, but also marriage within ethnic communities. But that would look even more problematic.
How should we respond then to the high rates of health and learning problems in communities like those in Bradford?
One important response is to be aware of the additional needs of those communities (Bradford has areas that are among the most deprived in the UK) and to ensure that the needs of children are addressed.
A second response is to provide education to families and to young people who are potentially marrying so that they are aware of the increased risks associated with cousin marriage and can make informed decisions.
Finally, there are more sophisticated and targeted ways of identifying risks for couples while respecting their reproductive rights. So-called expanded reproductive carrier screening could identify before they become pregnant, whether both partners in a couple are carriers for the same genetic illness. That could help them to decide whether to have children together, whether to use other techniques – such as IVF – to prevent genetic illness or to adopt. That expanded screening isn’t currently available on the NHS, but it could be made available to couples who are related.
We should be concerned about higher rates of illness in the children of parents who are related. But the ethical answer isn’t to ban them from getting married.
Dominic Wilkinson, Consultant Neonatologist and Professor of Ethics, University of Oxford
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Thanks for saying it – the slippery slope in this one is real, and I’m wondering what infringement of privacy and freedom would come with the process to enforce the ban. For instance, would we need to prove our relationship with our fiance/ee before marriage, so as to ascertain that we are not related?
I also think it is culturally insensitive, given that it is a certain community wherein it is traditional for cousins to get married – and by being that, is harmful, as it prohibits freedom in a discriminatory way.
Lastly, I think it is ableist – the ban will signal to people with learning and speech disabilities that they are unwanted, or a burden to society. Perhaps more attention and resources can be driven towards creating more disability-inclusive structural change.
This is also an argument for legalizing father-daughter, mother-son, sister-brother incest… after all, you know, the “identity problem.”
Prohibiting intra-primary-family incest, which inevitably leads to procreation, also prevents the existence of persons who would otherwise exist… with all their birth defects, but never mind.
Is banning such unions “eugenic”? Sure… just as encouraging abortion when the pregnant mother has taken thalidomide is “eugenic.” So?
But, “ineffective”? No… it prevents preventable birth defects.
Is it really necessary to point that out?
The recent tendency of the public power to infringe the private space is obvious.
The state penetrates our not only our gardens, our living rooms, our child rooms but also our bedrooms. Is this correct? Is the state wise enough to decide instead of an individual? How to treat my life is the matter of my decision, not politicians ….
So, for example, should individuals who are Covid positive then have the right to walk around unmasked and in everyone’s face?
There have to be limits to individual liberty, when harm to others is at stake.
Your unqualified claim that “How to treat my life is the matter of my decision, not politicians …” is indefensible as stated.
We shall differ between public and private.
The politics should treat the public issues like the rate of taxes, deciding if build hospital or stadium, deciding if trade with US or China. These decisions should be stated on some political ideology (right, left, green, conservative, liberal, feminist etc.). And the voters should chose one in fair election. This is democracy.
But to decide who I marry or if I can smoke in pub is neither matter of politics nor matter of political ideology.
Notice that any totalitarian ideology wanted to rule family and had the tendency to order how “correct” family should look like.
The example of Covid is false. Our disproportionate reaction on Covid has nothing in common with the public health or human rights. Our reaction was the circumstance of social media power and misuse of the public authorities that imposed blanket and not reasonable measures. BTW: The US House of Representatives recently declared that the face mask wearing was not justified by the scientific reasons.
This various and different opinions on anti-Covid measures should itself warn us about the situation in which the public power tends to impose the rules that disproportionately infringe the rights of the individuals. Anyway should individual who is any respiratory virus positive have right to leave his/her house. How far we want to go?
I completely agree with everything David Zimmerman said. The appeal to the nonidentity problem is both ill-conceived (Parfit must be turning on his grave) and inconsistent with the suggestion that they use IVF. If it does not matter, why discard any embryos? Of course, it matters. Some of these children will have lives of net suffering, and the same goes for their mothers, who (unlike their fathers) will be able to do little else in life but look after them, sometimes with very limited means or help from others.
It is, moreover, impossible to screen any possible problem that may result from inbreeding. Screening only rules out a limited number of well-known conditions. Not everything can be detected. And the same goes for the 6% figure, it only refers to some major, well documented conditions for which statistics exist but it does not cover all the problems that may result from inbreeding.
In any case, reducing the incidence of impairment from 6% to 3% in these often-disadvantaged communities is at least as good as reducing it from 3% to 0% outside those communities: Nobody would consider this negligible, and a pregnant woman certainly would not.
Why does a gorilla leave her beloved mother to venture alone in the forest once she is sexually mature? In species in which the females make a massive maternal investment, females are typically selective and refuse to have children with their relatives, and genetic tests show that they do not. This is why there is such an overlap between marring first cousins and arranged/coerced marriages and other sexist practices, and why outside those communities, it is extremely rare for independent women to freely chose to marry a cousin.
The norm, moreover, is to marry first cousins that are themselves the offspring of first cousins, sometimes for hundreds of years, creating much higher degrees of inbreeding than an occasional cousin marriage will cause. Robert Trivers’ genetics test showed such degree of similarity between a patriarch and his grandchildren that these men are practically cloning themselves at the expense of all the women who live in unwanted, unequal marriages looking after impaired children. This is why, as Trivers show in The Folly of Fools and subsequent works, honor crimes are amongst the most horrific. They have to be extraordinarily cruel to scare women into submission. Ending cousin marriage, will reduce forced marriages and honor crimes. So what “freedom” are we talking about here?
We must reduce the incidence of impairment and then give the few children who will still develop serious problems all the support they can possibly need, and give their mothers long breaks by sending qualified personnel to help them at public expense. And those who are not prepared to devote their lives to looking after impaired children should not be promoting their multiplication.
“Left wing political thinking has always sounded more attractive for all of us and above all for most intellectuals. Why? It offers clues. Or better said it seems to offer clues”. Roger Scruton said. But let us be always aware if we want to “invent” the receipts how to ensure or rather order happiness for the others. Because it is not really happiness. These are just our own visions how the other people should live. And those who does not fit these visions we tend to exclude.