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In Europe and America, marriage between cousins was once quite common; in the Middle East, South Asia and North Africa, it still is.
Every culture has its taboos, deeply rooted beliefs that certain practices are wrong…
Essentially, taboos are a kind of social control that tells us which behaviors are acceptable and which are not.
Taboos are part and parcel of culture, and what is considered repugnant in one society may be a permissible everyday practice in another.
Cousin marriage is quite common around the world, especially in countries in the Middle East, South Asia and North Africa.
Around 10% of families worldwide are headed by couples of second cousins or closer. This represents more than 750 million people.
If you look at a map of the world showing where cousin marriage is legal, you will see that it is legal in most countries in Europe, the Americas, Australia, parts of Africa and Asia.
But the map of cousin marriage laws in the United States looks like a patchwork.
In some states, including New York, California, and Florida, you can marry your first cousin without restriction. But in many other countries, such as West Virginia, Kentucky, and Texas, cousin marriage is completely prohibited.
In Arizona, Illinois, and Utah, you can only marry your cousin if one of you is sterile or both of you are over a certain age.
And in one state, Maine, you can only marry your cousin if you’ve had genetic counseling.
Why genetic counseling? If you ask Americans why marriage between cousins is bad, most of them will answer that it is because the couple’s children will have genetic diseases.
Risks of mixing identical genes
Wendy Chung, a geneticist at Columbia University in New York, studies genetic disorders, that is, cases where the DNA shows signs of abnormality.
Ms. Chung also counsels and treats families with genetic disorders.
“For me, genetics makes tremendous sense (…) And it’s very satisfying to be able to understand the science and help the people, the families involved,” she says.
As an embryo develops in the womb, genes can change in different ways and cause problems.
There are birth defects, for example when a part of the body does not develop properly, such as a cleft lip.
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Genetic counseling seeks to determine if there are any abnormal genes that can lead to birth defects in the child.
How does the rate of genetic diseases in descendants of first cousins compare to that of the general population?
“By simply deciding to have offspring, you have a 3-4% risk of having a child with one of the main types of problems. In a couple of first cousins, this risk is doubled,” says Ms Chung .
Depending on your situation, there are many reasons why you might want to marry your cousin.
First, there is the idea of keeping the wealth in the family. And then there is familiarity.
For those in an arranged marriage, it’s probably better to marry someone you’ve spent years with as a family than a man or woman you’ve only had a few encounters with.
In Europe and America, marriage between cousins was once quite common. People like Charles Darwin, Edgar Allan Poe and Albert Einstein married first cousins.
And it’s not just in the distant past. Former New York Mayor Rudolph Giuliani’s first wife was his second cousin.
abnormal genes
In general, marriage between cousins is quite safe. But in some specific populations or families, there may be more risk.
Chung says it’s due to a class of genetic conditions.
“There are certain conditions where it takes two for something to happen. You have two copies of your gene, one from your mother, the other from your father, and for certain diseases, it takes those changes genetics in both copies of the genes cause a problem,” she explains.
“If 50% of this gene is doing its job, you can be fine. But when you are 100% [anormal]this is where things go wrong,” she adds.
Ms. Chung talks regarding autosomal recessive conditions, and there are thousands of them.
Some are fairly well known and serious, such as sickle cell anemia, cystic fibrosis or spinal muscular atrophy.
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Elsa Einstein and Albert Einstein were cousins and married in 1919, both in second marriages, but no children were born on their wedding day.
Most people carry certain abnormal recessive genes. If you have one abnormal copy, you are fine, but if you have two abnormal copies, you have a disorder.
Thus, it is not necessary to be married to your cousin to have a child with a recessive disease.
However, “when you share 12.5% of your genetic information with your partner, there is an increased risk that you both carry a mutation in the same gene that you inherited from a common ancestor,” explains Ms Chung.
What if you are both carriers of the same recessive genetic disease?
This is when the child is most likely to be born with a genetic disease.
Inbred families
To determine the genetic risk of marrying a cousin, Chung says you don’t just have to look at that couple or family.
“It’s not just regarding first-cousin marriages, it’s really the broader demographic context in which this is happening,” she explains.
“In some communities, there may be intermarriage for generations. Whether it is an island, a village or a city, there may be a relatively high frequency of certain genetic variants in certain genes that confer an increased risk of disease”, informs the geneticist.
She claims that “in some royal families it was done to maintain power, to maintain wealth within the family.” “So it’s not just regarding sharing 12.5% of your genetic information. You’re actually potentially sharing a much larger fraction of your genetic information because of these multi-generational relationships,” Chung said.
Regina Peruggi is the first cousin of Ruldolph Giuliani. Married between 1968 and 1982, they had no children.
According to Chung, when a population has experienced many cousin marriages, the risk of having children with genetic disorders is higher.
When there are not many cousin marriages, this risk is much lower.
Geneticists cannot accurately calculate the risk of recessive conditions for all cousin marriages. Every family is different, every couple too.
To determine a couple’s risk, a geneticist will need to examine their genes to see if they both carry the same abnormalities.
This is especially important in communities where these disorders are most prevalent, such as the ultra-Orthodox Jewish communities in New York City, with which Ms. Chung works.
“A member of the community, Rabbi Eckstein, was unfortunately tragically affected along with his family, as he had several children with Tay-Sachs disease, which is fatal,” she says.
“To date, we have no treatment for this disease and children die before the age of five. And it can be stigmatizing to know that you have Tay-Sachs disease. If your family is affected by this issue, you may not be as desirable in terms of matching in the community,” adds the geneticist.
Matching is how most marriages are arranged in this community. And this cultural practice has become an opportunity to solve the problem of Tay-Sachs disease.
Rabbi Eckstein devised a plan for young people to take a genetic test before being matched. Carriers of Tay-Sachs disease would only be matched with non-carriers.
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When Edgar Allan Poe and Virginia Clemm, first cousins, married in 1836, he was 27 and she was 13.
“Culturally, it’s been extremely well accepted, well regarded, and this program has actually transformed the Orthodox Jewish community, in the sense that we don’t really see Tay-Sachs disease anymore,” Chung says.
So while marrying a cousin can be risky in some communities, overall the risk is not much higher than in the general population. And with the help of science – through genetic counseling and in vitro fertilization – communities can further minimize the risk of these recessive genes.
“It’s not acceptable”
The genetic risks of marrying your cousin have been exaggerated, says Mona Chalabi in her podcast. And with modern science, cousin marriage is probably safer than ever.
Most bans on cousin marriage in the United States were in effect from the mid-19th century to the early 20th century.
But in Texas, the ban is much more recent: it dates back to 2005. It was in response to the arrival of a fundamentalist Mormon sect known for its child abuse.
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Emma Wedgwood and her cousin Charles Darwin photographed in their youth. They had 10 children.
There, the marriage between cousins is added to the marriage between children. The state representative who proposed the bill said, “Cousins don’t marry, just like siblings don’t marry. And when that happens, you get a bad score. That’s not not acceptable.”
Texas law codifies the stigma of cousin marriage and reinforces taboos.
Who are taboos for and what are they really trying to do? asks Mona Chalabi. Cousin marriage is widely practiced in non-white cultures, and some of the prejudice once morest it is simply racist, she says.
If Arabs, North Africans and South Asians do it, some people will think it’s “disgusting”.
But maybe you like your cousin, and maybe following reading this you can ask him out, Chalabi comments.
