This is controversial and will remind some people why they hate blogs. But it’s been nagging at me for months, so I’m saying it anyway.
For the past few months I’ve seen a lot of right-wing content circulating online about cousin marriage in the UK — specifically whether it should be banned.
Leaving aside the long history of cousin marriage in the British royal family and aristocracy, most of this debate focuses on Pakistani Muslims. The claim is that higher rates of cousin marriage lead to higher rates of genetic disorders, which in turn create higher welfare and healthcare costs.
These posts are usually accompanied by lurid photographs purporting to show large families of disabled Muslims, along with attacks on Labour MPs accused of defending “cultural practices”.
Unpleasant as this material is, there is some evidence behind the claims.
What the evidence actually says
Born in Bradford is a long-running clinical study tracking over 60,000 residents. It’s the best UK dataset we have on cousin marriage.
The basic science is straightforward:
- Unrelated couples face a 2–3% risk of genetic disorders
- First cousins face a 4–6% risk
So yes — the risk doubles, but from a low baseline.
The Bradford data broadly confirms this. It also found evidence that children born to cousin couples performed less well in speech, language and some developmental markers, and struggled at school.
This isn’t the apocalyptic picture painted online, but it does lend some support to the core claim.
The big caveat
Born in Bradford is proper clinical research. Its raw data is not public.
That means journalists, influencers and sceptics like me are all relying on second-hand summaries. That makes exaggeration easier — and proper scrutiny harder.
Which brings me to my own scepticism.
My NHS experience
Years ago, while working in the NHS, I was involved in a Government Health Action Fund project looking at young-onset dementia on Teesside.
An epidemiological model suggested around 100 undiagnosed cases.
We found double that number in East Cleveland alone.
There were dramatic clusters in places like:
- Loftus
- Skinningrove
- Boulby
White working-class, rural, insular communities.
The geographical distribution looked eerily similar to the Bradford genetic data. This wasn’t the only time I saw this pattern in the North East. I repeatedly encountered disease clusters that looked a lot like a lack of genetic diversity.
None of these areas had Pakistani-style cousin marriage.
But they did share something else:
People rarely married outsiders.
Paternity data: another piece of the puzzle
Around the same time, Newcastle University ran a sibship study into rheumatoid disease.
One striking finding:
In parts of Newcastle, nearly 20% of people had a biological father who wasn’t the man on their birth certificate.
Later, at CMEC/CSA, I ran the DNA testing contract.
In child maintenance disputes:
Up to 30% involved a different biological father than recorded.
There are caveats — disputes inflate the numbers, and the East End isn’t Gosforth — but the conclusion is unavoidable:
There is far more biological overlap in some UK communities than we like to admit.
The blind spot
We look for consanguinity in Muslim communities — so we find it.
We don’t look elsewhere — so we don’t.
That doesn’t mean it isn’t there.
This would explain why some white working-class communities show:
- Similar patterns of genetic illness
- Similar educational underperformance
to Pakistani communities in Bradford.
We already know this happens
We see genetic clustering elsewhere in the UK:
- Shetland – Batten disease
- South Wales – kidney disorders
- Lancashire – Zellweger syndrome
All caused by small, closed gene pools.
Observed vs actual incidence
There’s a difference between:
- Observed incidence – what gets recorded
- Actual incidence – what really exists
In Bradford we measure it.
Elsewhere we don’t.
So we conclude:
“This is a Pakistani problem.”
That may be a measurement problem, not a reality problem.
The uncomfortable ending
When David Cameron asked Frank Field to review the benefits system, he spoke to CMEC.
Field claimed:
Levels of consanguinity in white working-class communities were far higher than anyone realised.
He even suggested using CSA powers to compel DNA testing to prevent people unknowingly having children with close relatives.
At the time I thought he was mad.
Now I’m not so sure.
Final note
None of this excuses racism.
None of it justifies demonising Muslims.
But pretending this is only a Muslim issue
is just as dishonest.
Genetics doesn’t care about culture.
It cares about who you reproduce with.
And that’s an awkward conversation Britain has barely started.
https://www.nature.com/articles/s41467-024-51604-2
https://www.bmj.com/content/387/bmj.q2181
Yeah…
I’d keep this one off the local facebook groups 😁
Please share it! I am blocked from posting on most of them!!
Good point on how isolated rural white communities have more consanguinity than we’d expect, but I still don’t see how we could get as much inadvertently in such communities, as we do in (eg) Pakistani communities which deliberately marry cousins!
(And intentional cousin marriage is damaging not just medically but also culturally, driving the oppression of women and splintering the population into self-contained clans at odds with one another.)
And the most damaging (FBD) form of cousin marriage — that globally is almost unique to cultures from lands formerly part of the Arab Caliphate — is something that would almost never happen by accident in a Western culture, because the would-be bride and groom would have the same surname — in fact that’s probably precisely why surnames were invented in the first place!
You are assuming that people outside the Pakistani community have the correct paternal surname. The question is – how many people don’t have the correct father on the birth certificate? Which would mean that people don’t have the surname of their biological father?
You mention low levels of genetic diversity in East Cleveland (presumably because those villages are isolated): it wouldn’t surprise me if “Category D” ex-pit villages in County Durham were as bad or worse!