It is estimated that at least 55% of British Pakistanis are married to first cousins and the tradition is also common among some other South Asian communities and in some Middle Eastern countries. But there is a problem: marrying someone who is themselves a close family member carries a risk for children, a risk that lies within the code of life, inside our genes. Communities that practice cousin marriage experience higher levels of some very rare but very serious illnesses known as recessive genetic disorders.
Such unions are seen as strong because they build on tight family networks and family events gets better because the in-laws are already related to each other and have the same family history. But the statistics for recessive genetic illness in cousin marriages is serious as British Pakistanis are 13 times more likely to have children with genetic disorders than the general population.
Cousin marriage is marriage between two cousins. This kind of marriage is highly stigmatized today in the West, but it does account for over 10% of marriages worldwide as it is common in the Middle East, where in some nations they account for over half of all marriages.
According to Professor Robin Fox of Rutgers University, it is likely that 80% of all marriages in history have been between second cousins or closer. It is generally accepted that the founding population of Homo sapiens was small, anywhere from 700 to 10,000 individuals. Rates of first-cousin marriage in the United States, Europe, and other Western countries like Brazil have declined since the 19th century, though even during that period they were not more than 3.63% of all unions in Europe. But in many other world regions cousin marriage is still strongly favoured: in the Middle East some countries have seen the rate rise over previous generations, and one study finds quite stable rates among Indian Muslims over the past four decades.
Cousin marriage has often been chosen to keep cultural values and ensure the compatibility of spouses, preserve familial wealth, sometimes via advantages relating to dowry or bride price. Other reasons may include geographic proximity, tradition, strengthening of family ties, maintenance of family structure, a closer relationship between the wife and her in-laws, greater marital stability and durability, ease of prenuptial negotiations, enhanced female autonomy, the desire to avoid hidden health problems and other undesirable traits in a lesser-known spouse, and romantic love.
The United States has the only bans on cousin marriage in the Western world. As of February 2010[update], 30 U.S. states prohibit most or all marriage between first cousins together with other 6 states.
Cousin marriage was legal in all US states in the Union prior to the Civil War. However, according to Kansas sociology professor Martin Ottenheimer, after the Civil War the main purpose of marriage prohibitions was increasingly seen as less maintaining the social order and upholding religious morality and more as safeguarding the creation of fit offspring. By the 1870s, Lewis Henry Morgan was writing about “the advantages of marriages between unrelated persons” and the necessity of avoiding “the evils of consanguine marriage.” Cousin marriage to Morgan, and more specifically parallel-cousin marriage, was a remnant of a more primitive stage of human social organization. Morgan himself had married his mother’s brother’s daughter in 1851.
In 1846 the Governor of Massachusetts appointed a commission to study “idiots” in the state which implicated cousin marriage as being responsible for idiocy. Within the next two decades numerous reports appeared coming to similar conclusions, including for example by the Kentucky Deaf and Dumb Asylum, which concluded that cousin marriage resulted in deafness, blindness, and idiocy. Perhaps most important was the report of physician S.M. Bemiss for the American Medical Association, which concluded “that multiplication of the same blood by in-and-in marrying does incontestably lead in the aggregate to the physical and mental depravation of the offspring.”
These developments led to thirteen states and territories passing cousin marriage prohibitions by the 1880s. Though contemporaneous, the eugenics movement did not play much direct role in the bans, and indeed George Louis Arner in 1908 considered them a clumsy and ineffective method of eugenics, which he thought would eventually be replaced by more refined techniques. Ottenheimer considers both the bans and eugenics to be “one of several reactions to the fear that American society might degenerate.” In any case, by the period up until the mid-1920s the number of bans had more than doubled. Since that time, the only three states to successfully add this prohibition are Kentucky in 1943, Maine in 1985, and Texas in 2005. The NCCUSL unanimously recommended in 1970 that all such laws should be repealed, but no state has dropped its prohibition since the mid-1920s.
Only Austria, Hungary, and Spain banned cousin marriage throughout the 19th century, with dispensations being available from the government in the last two countries. Protestant, the Church of Sweden didn’t ban first-cousin marriage until 1680 and required dispensation until 1844. England maintained a small but stable proportion of cousin marriages for centuries, with proportions in 1875 estimated by George Darwin at 3.5% for the middle classes and 4.5 % for the nobility, though this has declined to under 1 % in the 20th century. Queen Victoria and Prince Albert were a preeminent example.
The 19th century academic debate on cousin marriage evolved differently in Europe than it did in America. The first-cousin marriage was legal in ancient Rome from at least the Second Punic War (218–201 BC) to its ban by the Christian emperor Theodosius I in 381 AD in the west and until after Justinian (d. 565 AD) in the east.
Early Catholic marriage rules forced a sharp change from earlier norms in order to deny heirs to the wealthy and therefore increase the chance they would will their property to the Church.
The Middle East has uniquely high rates of cousin marriage among the world’s regions. Saudi Arabia, have rates of marriage to first or second cousins that may exceed 50%, Iraq was estimated in one study to have a rate of 33%, and figures for Iran and Afghanistan have been estimated in the range of 30–40%. Though on the lower end, Egypt and Turkey nevertheless have rates above 20%.
All states in the Persian Gulf currently require advance genetic screening for all prospective married couples. Qatar was the last Gulf nation to institute mandatory screening in 2009, mainly to warn related couples who are planning marriage about any genetic risks they may face. The current rate of cousin marriage there is 54%, an increase of 12–18% over the previous generation. A report by the Dubai-based Centre for Arab Genomic Studies (CAGS) in September 2009 found that Arabs have one of the world’s highest rates of genetic disorders, nearly two-thirds of which are linked to consanguinity. Research from CAGS and others suggests consanguinity is declining in Lebanon and Egypt and among Palestinians, but is increasing in Morocco, Mauritania and Sudan.
Dr. Ahmad Teebi, a genetics and pediatrics professor at Weill Cornell Medical College in Qatar, links the increase in cousin marriage in Qatar and other Gulf states to tribal tradition and the region’s expanding economies. “Rich families tend to marry rich families, and from their own – and the rich like to protect their wealth,” he said. “So it’s partly economic, and it’s also partly cultural.” In regard to the higher rates of genetic disease in these societies, he says: “It’s certainly a problem,” but also that “The issue here is not the cousin marriage, the issue here is to avoid the disease.”
Cousin marriage rates from most African nations outside the Middle East are unknown. It is however estimated that 35–50% of all sub-Saharan African populations either prefers or accept cousin marriages. In Nigeria, the most populous country of Africa, the three largest tribes in order of size are the Hausa, Yoruba, and Igbo. Muslim Hausa practice cousin marriage preferentially, and polygamy is allowed if the husband can support multiple wives. Divorce can be accomplished easily by either the male or the female, but females must then remarry. Even for a man, lacking a spouse is looked down upon. Baba of Karo’s first of four marriages was to her second cousin. She recounts in the book that her good friend married the friend’s first cross cousin.
The Yoruba people are split between Islam and Christianity. A 1974 study analyzed Yoruba marriages in the town Oka Akoko, finding that among a sample of marriages having an average of about three wives. These included not only cousin marriages but also uncle-niece unions. Reportedly it is a custom that in such marriages at least one spouse must be a relative, and generally such spouses were the preferred or favourite wives in the marriage and gave birth to more children. Finally, the Igbo people of southern Nigeria specifically prohibit both parallel- and cross-cousin marriage, though polygamy is common. Men are forbidden to marry within their own patrilineage or those of their mother or father’s mother and must marry outside their own village. Igbo are almost entirely Christian, having converted heavily under colonialism
In Ethiopia the ruling Christian Amhara people were historically rigidly opposed to cousin marriage, and could consider up to third cousins the equivalent of brother and sister, with marriage at least ostensibly prohibited out to sixth cousins. A man marrying a former wife’s “sister” was seen as incest, and conversely for a woman and her former husband’s “brother.” Though Muslims make up over a third of the Ethiopian population, and Islam has been present in the country since the time of Muhammad, cross-cousin marriage is very rare among most Ethiopian Muslims.
Attitudes in India on cousin marriage vary by region and culture. For Muslims it is acceptable and legal to marry a first cousin but for Hindus it may be illegal under the 1955 Hindu Marriage Act, though the specific situation is more complex. The Hindu Marriage Act makes cousin marriage illegal for Hindus with the exception of marriages permitted by regional custom. Cousin marriage is proscribed and seen as incest for Hindus in north India. In fact it may even be unacceptable to marry within one’s village or for two siblings to marry partners from the same village but in south India it is common for Hindu’s to marry cross cousins, with matrilateral cross-cousin (mother’s brother’s daughter) marriages being especially favoured. In Mumbai, studies done in 1956 showed 7.7% of Hindus married to a second cousin or closer in contrast to the northern city of New Delhi where only 0.1% of Hindus were married to a first cousin during the 1980s.
India’s Muslim minority represents about 12% of its population (excluding Jammu and Kashmir) and has an overall rate of cousin marriage of 22% according to a 2000 report. Most Muslim cousin marriages were between first cousins with a rate of 20%.
There has been a great deal of debate in the past few years in the United Kingdom about whether to discourage cousin marriages through government public relations campaigns or ban them entirely. The debate has been prompted by a Pakistani immigrant population making up 1.5% of the British population, of whom about 55% marry a first cousin. There is evidence that the rate of cousin marriage has increased among British Pakistanis from rates in their parents’ generation. Most British Pakistani marriages are arranged, but these can be of two types: conventionally arranged marriages where the bride and groom have little or no say, and what some British Pakistanis describe as “arranged love marriages” where the bride and groom play an important role.
In the East, South Korea is especially restrictive with bans on marriage out to third cousins, with all couples having the same surname and region of origin having been prohibited from marrying until 1997. Taiwan, North Korea, and the Philippines also prohibit first-cousin marriage. It is allowed in Japan, though the incidence has declined in recent years. China has banned it since passing its 1981 Marriage Law, yet there is a conspicuous lack of data on actual cousin marriage rates there.
Recent 2001 data for Brazil indicates a rate of cousin marriage of 1.1%, down from 4.8% in 1957. For example, in São Paulo in the mid-19th century the rate of cousin marriage apparently was 16%, but a century later it was merely 1.9%.
Social aspects of cousin marriages
People may think that cousin marriages are more common among those of low socioeconomic status, among the illiterate and uneducated, and in rural areas due to the dowries and bridewealths that exist, but some societies also report a high prevalence among land-owning families and the ruling elite: here the relevant consideration is thought to be keeping the family estate intact over generations.
In South Asia, rising demands for dowry payments have caused economic hardship and have been linked to “dowry deaths” in a number of North Indian states. The increasing number of cousin marriages in the West may also occur as a result of immigration from Asia and Africa and some observers have concluded that the only new forces that could discourage such unions are government bans like the one China enacted in 1981.
In April 2002, the Journal of Genetic Counseling released a report which estimated the average risk of birth defects in a child born of first cousins at 1.7–2.8% over an average base risk for non-cousin couples of 3%, or about the same as that of any woman over age 40. In terms of mortality, a 1994 study found a mean excess pre-reproductive mortality rate of 4.4%, while another study published in 2009 suggests the rate may be closer to 3.5%. Put differently, first-cousin marriage entails a similar increased risk of birth defects and mortality as a woman faces when she gives birth at age 41 rather than at 30. Critics argue that banning first-cousin marriages would make as much sense as trying to ban childbearing by older women.
In Pakistan, where there has been cousin marriage for generations and the current rate may exceed 50%, one study estimated infant mortality at 12.7 % for married double first cousins, 7.9 % for first cousins, 9.2 % for first cousins once removed/double second cousins, 6.9 % for second cousins, and 5.1 percent among nonconsanguineous progeny. Among double first cousin progeny, 41.2 % of prereproductive deaths were associated with the expression of detrimental recessive genes, with equivalent values of 26.0, 14.9, and 8.1 % for first cousins, first cousins once removed/double second cousins, and second cousins respectively.
For example because the entire Amish population is descended from only a few hundred 18th century German-Swiss settlers, the average coefficient of inbreeding between two random Amish is higher than between two non-Amish second cousins. First-cousin marriage is taboo among Amish but they still suffer from several rare genetic disorders. In Ohio’s Geagua County, Amish make up only about 10 % of the population but represent half the special needs cases. Similar disorders have been found in the highly polygamous FLDS, who do allow first-cousin marriage and of whom 75 to 80 % are related to two 1930s founders.
A BBC report reported about Pakistanis in Britain where 55% of whom had married a first cousin and many children come from repeat generations of first-cousin marriages. The report stated that these children were 13 times more likely than the general population to produce children with genetic disorders, and one in ten children of first-cousin marriages in Birmingham either died in infancy or would develop a serious disability. The BBC story contained an interview with Myra Ali, whose parents and grandparents were all first cousins. She has a very rare recessive genetic condition, known as Epidermolysis bullosa which will cause her to lead a life of extreme physical suffering, limited human contact and probably an early death from skin cancer. Knowing that cousin marriages increase the probability of recessive genetic conditions, she is against the practice. Finally, in 2010 the Telegraph reported that cousin marriage among the British Pakistani community resulted in 700 children being born every year with genetic disabilities.
The increased mortality and birth defects observed among British Pakistanis may, however, have another source besides current consanguinity. Genetic effects from cousin marriage in Britain are more obvious than in a developing country like Pakistan because the number of confounding environmental diseases is lower. Increased focus on genetic disease in developing countries may eventually result from progress in eliminating environmental diseases there as well.
Public Health in Norway published in March 2007 a research on intermarriage in Norway. The report identifies both the prevalence of intermarriage and the medical consequences for the children. The analysis was done on the basis of data from the Medical Birth Registry, Statistics Norway, Population Register and the Cause of Death Register of data for all persons born in Norway from 1967 to 2005 because Norway is the only country in the world that keeps the statistic numbers between the parents of all born babies. These were the key findings:
Prevalence of intermarriage:
- In Norway, the most widespread intermarriage can be found among people of Pakistani origin. In first-generation immigrants from Pakistan intermarriage is 43.9% of all children born of parents who are cousins, and the total intermarriage ratio is 54.4%.
- Among the descendants of first generation immigrants from Pakistan, the proportion of cousin pairs 35.1%, and the total intermarriage ratio 46.5%. Interbreeding units are therefore somewhat lower than in the parental generation.
- Intermarriage-shares seem to be heading down in the Norwegian-Pakistani population, both first generation immigrants and descendants.
- Intermarriage is relatively common also among people with origins from Turkey, Iraq, Iran, Sri Lanka, Morocco and Somalia.
- For people of Norwegian origin, intermarriage is very rare, but it used to be more common a few decades back. This particularly applies to second cousin marriages. In those of Norwegian origin is 0.1% of parental pairs cousins and second cousins 0.4% (in the period from 1967 to 2005).
Medical risks of intermarriage
Intermarriage leads to increased risk of stillbirth, infant death and congenital malformations. In addition, there is an increased risk of death right up to adulthood among children of intermarried parents.
For children of cousin marriage is the increase of risk in the following order:
- Stillbirth: 60%
- Deaths during the first year: 150%
- Congenital malformations: 100%
- Deaths from the age of one year and up to adulthood: 75%
These findings are statistically reliable, and not the result of random variation.
The significance of intermarriage for public health
Since intermarriage is rare in the population as a whole, intermarriage does little for public health in Norway, however, it is a major cause of illness and death among children in the country groups where intermarriage is common.
One must always bear in mind that most children of intermarriage, marriage is healthy and completely normal. Illness and death affects only a small minority of them.
Jewish communities affected by Tay-Sachs
Tay–Sachs disease (TSD, also known as GM2 gangliosidosis or Hexosaminidase A deficiency) is an autosomal recessive genetic disorder. In its most common variant, known as infantile Tay–Sachs disease, it causes a relentless deterioration of mental and physical abilities that commences around 6 months of age and usually results in death by the age of 4. Tay-Sachs is caused by a genetic defect in a single gene with one defective copy of that gene inherited from each parent. The disease occurs when harmful quantities of gangliosides accumulate in the nerve cells of the brain, eventually leading to the premature death of those cells. There is currently no cure or treatment but the Tay–Sachs disease is rare.
Tay-Sachs disease was named after British ophthalmologist Warren Tay, who first described the red spot on the retina of the eye in 1881, and the American neurologist Bernard Sachs of Mount Sinai Hospital, New York who described the cellular changes of Tay-Sachs and noted an increased prevalence in the Eastern European Jewish (Ashkenazi) population in 1887. Research in the late 20th century demonstrated that Tay–Sachs disease is caused by a genetic mutation on the HEXA gene on chromosome 15. These mutations reach significant frequencies in several populations. French Canadians of southeastern Quebec have a carrier frequency similar to Ashkenazi Jews, but they carry a different mutation. Many Cajuns of southern Louisiana carry the same mutation that is most common in Ashkenazi Jews. Most HEXA mutations are rare, and do not occur in genetically isolated populations. The disease can potentially occur from the inheritance of two unrelated mutations in the HEXA gene.
Millions of Ashkenazi Jews have been screened as Tay-Sachs carriers since carrier testing began in 1971. Jewish communities, both in and outside of Israel, embraced the cause of genetic screening from the 1970s on and the increasing number of Tay–Sachs disease led Israel to become the first country to offer free genetic screening and counseling for all couples making Israel a leading center for research on genetic disease. Both the Jewish and Arab/Palestinian populations in Israel contain many ethnic and religious minority groups, and Israel’s initial success with Tay–Sachs disease has led to the development of screening programs for other diseases.
Tay-Sachs has sometimes created an impression that Jews are more susceptible to genetic disease than other populations. Sheila Rothman and Sherry Brandt-Rauf, of Columbia University’s Center for the Study of Society and Medicine, have criticized this emphasis on ethnic identity in the study of disease. When several breast cancer mutations were discovered in the 1990s, the TSD model was applied, both consciously and inadvertently. Researchers had initially focused on breast cancer cluster families, not on ethnic groups. But because thousands of stored DNA samples were available from Tay-Sachs screening, researchers were quickly able to estimate the frequency of newly discovered mutations in Ashkenazi Jewish populations.
Inbreeding in the Royal and Nobel families
The family relationships of royalty are usually well known to be highly inbreeded. Royal intermarriage was mostly practised to protect property, wealth, and position.
- In ancient Egypt, royal women carried the bloodlines and so it was advantageous for a pharaoh to marry his sister or half-sister. Normally the old ruler’s eldest son and daughter (who could be either siblings or half-siblings) became the new rulers. All rulers of the Ptolemaic dynasty from Ptolemy II were married to their brothers and sisters, to keep the Ptolemaic blood “pure” and to strengthen the line of succession. Cleopatra VII (also called Cleopatra VI) and Ptolemy XIII, who married and became co-rulers of ancient Egypt following their father’s death, are the most widely known example of brother and sister marriage.
The family-tree of Charles II of Spain shows an extraordinary number of uncle-niece and cousin unions of varying degrees that can be seen on the picture.
- Among European monarchies Jean V of Armagnac formed a rare brother-sister relationship. Also other royal houses, such as the Wittelsbachs had marriages among aunts, uncles, nieces, and nephews. The British royal family had several marriages as close as the first cousin, but none closer.
- The most famous example of a genetic disorder aggravated by royal family intermarriage was the House of Habsburg, which inmarried particularly often. Famous in this case is the Habsburg jaw/Habsburg lip/Austrian lip typical for many Habsburg relatives over a period of 6 centuries. The condition progressed through the generations to the point that the last of the Spanish Habsburgs, Charles II of Spain, could not properly chew his food.
- Besides the jaw deformity, Charles II also had a huge number of other genetic physical, intellectual, sexual, and emotional problems. It is speculated that the simultaneous occurrence in Charles II of two different genetic disorders: combined pituitary hormone deficiency and distal renal tubular acidosis could explain most of the complex clinical profile of this king, including his impotence/infertility which in the last instance led to the extinction of the dynasty.
- The most famous genetic disease that circulated among European royalty was haemophilia. Because the progenitor, Queen Victoria, was in a first cousin marriage, it is often mistakenly believed that the cause was consanguinity, however, this disease is generally not aggravated by cousin marriages, although rare cases of haemophilia in girls (though not including Victoria) are thought to result from the union of haemophilic men and their cousins.
- Intermarriage within European royal families has declined in relation to the past. Inter-nobility marriage was used as a method of forming political alliances among elite power-brokers and these ties were often sealed only upon the birth of progeny within the arranged marriage. Marriage was seen as a union of lines of nobility, not of a contract between individuals as it is seen today.
- Some Peruvian Sapa Incas married their sisters. The Inca had an unwritten rule that the new ruler must be a son of the Inca and his wife and sister. He then had to marry his sister (not half-sister), which ultimately led to the catastrophic Huáscar’s reign, culminating in a civil war and then fall of the empire.
When we look at the Norwegian history, marriage between cousins was rare and attempted to be prohibited in 1687 but the exception was the royals. They married relatives to build alliances, and ensure values and positions. It is not different from the today’s cousin marriages except the only difference was that the royal house had a stronger fundamental superstructure that was at the family’s superiority. Monarchical thinking assumes that your place in society is God-given and that your family is predetermined.
King Olav V and Queen Maud of Norway
To keep the heritage in their own hands, the Spanish Habsburgs started to marry more and more within the family. The result was that the lethal inbreeding within a few generations brought the male succession to destruction with 11 royal marriages in 200 years. 9 of these were intermarriages including two marriages between uncles and nieces and four between cousins. As a consequence of this, the Habsburgs suffered stillbirths and deaths of babies. Between 1527 and 1661 there was born 34 children and of these, 10 died before the age of 1 year. Another 17 died before the age of 10.
The Habsburgs last king, Carlos II, was born in 1661 and the Spaniards called him El hechizado, the enchanted. He had a large head and was relatively weak as a baby. He did not learn to speak before he turned four, and learned to walk when he was eight years old and stayed weak and very thin. His first and second wife claimed he was impotent and he would vomit and suffer from diarrhea. As a 30-year-old, King Carlos looked like he was an old man. He also couldn’t manage to bring an heir so the Halsburg Dynasty died with him in 1700.
Scientists have calculated that 25.4% of his gene variants were inherited in double dose and they believe he was hit by two genetic diseases that today are known as CPHD and distal renal tubular acidos (dRTA).
The Danish royal house was struggling with similar problems. Early in the 1800s did not King. Several diseases spread in the European royal houses of the 1800s and the British Queen Victoria’s descendants were affected by haemophilia resulting in her son Leopold death of the disease as 30-year-old. Her daughters, Princess Beatrice and Princess Alice brought the disease to the European royal houses.
Porphyria is another “royal disease” and the British king George III (1760 to 1820) was known as “Mad George” for his madness. Two professors of molecular genetics, Martin Warren and David Hunt of the University of London, examined in the book Purple Secret (1998) a thesis that George III’s illness was porphyria. They followed “Mad George” s genes down to today’s royals, and estimated that the Queen’s cousin William, who died in 1972, suffered from the disease. Also porphyria was brought further into the European royal families.
Norwegian Princess Astrid has been open to and told how she has experienced it to be dyslexic, like King Olaf was and the Princess’ five children also struggling with this problem.
In contrast, Swedish King Carl Gustaf, the Crown Princess Victoria and her brother Prince Carl Philip has been open with the disorder.
Camilla Stoltenberg of Public Health in Norway explains:
“If you inherit the gene from one parent, you may get a slight degree of the condition. Inherit it from both mother and father, the stronger the disposition, and then you can get a more serious disorder.” What then is the relationship between intermarriage and dyslexia?
“The chance that you get two identical copies of a gene is higher. This is also true for genes that predispose to dyslexia. And since dyslexia is probably conditioned by many genes, it is also a greater chance that you may have received two copies of several of the dysleksidisponerende genes,” she says.