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History
In earlier times, and still today in some cultures, it was relatively common for cousins to marry. 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.[10]
Cousin marriage has often been chosen to keep cultural values intact through several generations, ensure the compatibility of spouses, and preserve familial wealth, sometimes via advantages relating todowry or bride price. Other reasons 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, and romantic love. Many such marriages are arranged and facilitated by other extended family members.[11][10][2]
[edit]United 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. Indeed, writers such as Noah Webster and ministers like Philip Milledoler and Joshua McIlvaine helped lay the groundwork for such viewpoints well before 1860. This led to a gradual shift in concern from affinal unions, like those between a man and his deceased wife's sister, to consanguineous unions. 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," withdrawal from which would "increase the vigor of the stock." Cousin marriage to Morgan, and more specifically parallel-cousin marriage, was a remnant of a more primitive stage of human social organization.[12] Morgan himself had married his mother's brother's daughter in 1851.[13]
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." Despite being contradicted by other studies like those of George Darwin and Alan Huth in England and Robert Newman in New York, the report's conclusions were widely accepted.[14]
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."[15] In any case, by the period up until the mid-1920s the number of bans had more than doubled.[7] Since that time, the only three states to successfully add this prohibition are Kentucky in 1943, Maine in 1985, and Texas in 2005. Significantly, no state has dropped its prohibition in that period.[1]
[edit]Europe
Only Austria, Hungary, and Spain banned cousin marriage during the 19th century, with dispensations being available from the government in the last two countries.[16] England had maintained a small but stable proportion of cousin marriages for centuries, with proportions in 1875 estimated by George Darwin at 3.5 percent for the middle classes and 4.5 percent for the nobility, though this has declined to under 1 percent in the 20th century.[17] A preeminent example was Queen Victoria and Prince Albert.
The 19th century academic debate on cousin marriage evolved differently in Europe than it did in America. Despite the writings of Scottish deputy commissioner for lunacy Arthur Mitchell that cousin marriage had injurious effects on offspring, these conclusions were largely contradicted by researchers like Alan Huth and George Darwin.[18] (At one point Mitchell had claimed that inbreeding in Scottish fishing communities led to a lower average hat size of six and seven-eighths, a quarter inch less than their more outbred neighbors.)[19] In fact, Mitchell's own data did not support his hypotheses, prompting him to later speculate that the dangers of consanguinity might be partly overcome by proper living. Later studies by George Darwin found only much smaller effects that closely resemble those estimated today, and perhaps in response to his son's work, Charles Darwin eventually withdrew some earlier musings that cousin marriage might pose an evolutionary risk. In the end, when a question about cousin marriage was considered in 1871 for the census, according to George Darwin it was rejected "amid the scornful laughter of the House, on the grounds that the idle curiosity of philosophers was not to be satisfied."[20]
First-cousin marriage was legal in the late Roman Republic and the Roman Empire, though it was not habitual, and may have been banned in the early Republic.[5] For some prominent examples, such as the marriage of Octavian's daughter to his sister's son, see the Julio-Claudian family tree. Marcus Aurelius also married his maternal first cousin Faustina the Younger and had 13 children. Cousin marriage was more frequent in Ancient Greece:[5] for example, the Spartan King Leonidas I, who is depicted in the film 300, married his half-niece.
[edit]Middle East
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Many of the love stories included in The Thousand and One Nights depict love between first cousins.[citation needed] Also, Xerxes I of Persia was the offspring of third cousins.[21] He is depicted in the film300.
[edit]China
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In ancient China, marriage to a father's brother's daughter was not permitted, but other types of cousin marriage were.[4]
[edit]Current status
Slightly over 10% of all marriages worldwide are estimated to be between second cousins or closer.[2] As of 2001, here is one estimate for the percentages of world population living in countries with various levels of consanguineous marriage: less than 1% consanguinity, 18%, 1-10% consanguinity, 47%, 10-50+% consanguinity, 17%, and unknown, 18%.[11]
[edit]United States
Further information: Cousin marriage case law in the United States
The United States has the only bans on cousin marriage in the Western world.[22][23] The US also prohibits first-cousin-once-removed marriages in six states.[24] For example, Ohio only allows marriage between those "not nearer of kin than second cousins."
Data on cousin marriage in the United States is sparse. It was estimated in 1960 that 0.2% of all marriages between Roman Catholics were between first or second cousins, but no more recent nationwide studies have been performed.[25] It is unknown what proportion of that number were first cousins, which is the group facing marriage bans. To contextualize the group's size, note that the total proportion of interracial marriages in 1960, the date of the last census before the end of anti-miscegenation statutes, was 0.4%, while the proportion of black-white marriages was 0.13%.[26] Public opinion polling on whether first-cousin marriage should be legal is nonexistent. While recent studies have cast serious doubt on whether cousin marriage is as dangerous as is popularly assumed, professors Diane B. Paul and Hamish G. Spencer speculate that legal bans persist in part due to "the ease with which a handful of highly motivated activists—or even one individual—can be effective in the decentralized American system, especially when feelings do not run high on the other side of an issue."[27]
Among supporters of repealing the laws, perhaps the largest group is Cousin Couples, which describes itself as "the world's primary resource for romantic relationships among cousins including cousin marriage." This group likens laws against cousin marriage to the anti-miscegenation laws of decades past.[6] Their website includes information on state and international laws, world religious viewpoints, famous cousin couples and the genetic risk due to cousin marriage. It also includes a message board with several messages posted daily as of November 2009, which allows cousin couples to provide each other with emotional support, share pictures and love stories, and comment on the legal situation.[28]
A bill to repeal the ban on first-cousin marriage in Minnesota was introduced by Phyllis Kahn in 2003, but it died in committee. By training Kahn is a biophysicist and holds a PhD from Yale. Republican Minority Leader Marty Seifert criticized the bill in response, saying it would "turn us into a cold Arkansas."[29] According to the University of Minnesota's The Wake, Kahn was aware the bill had little chance of passing but introduced it anyway to draw attention to the issue. She reportedly got the idea after learning that cousin marriage is an acceptable form of marriage among some cultural groups that have a strong presence in Minnesota, namely the Hmong and Somali.[30]
In contrast, Maryland delegates Henry B. Heller and Kumar P. Barve sponsored a bill to ban first-cousin marriages in 2000.[31] (Barve later became Majority Leader.) It got further than Kahn's bill, passing the House of Delegates by a vote of 82 to 46, but then died in the state Senate. In response to the 2005 marriage of Pennsylvanian first cousins Eleanor Amrhein and Donald W. Andrews Sr. in Maryland, Heller said that he might resurrect the bill because such marriages are "like playing genetic roulette."[8]
Texas actually did pass a ban on first-cousin marriage the same year as Amrhein and Andrews married, evidently in reaction to the presence of the polygamous FLDS. Texas Representative Harvey Hilderbran, whose district includes the main FLDS compound, authored an amendment[32] to a child protection statute to both discourage the FLDS from settling in Texas and to "prevent Texas from succumbing to the practices of taking child brides, incest, welfare abuse and domestic violence."[33] While Hilderbran stated that he would not have authored a bill solely to ban first-cousin marriage, he also said in an interview that "Cousins don’t get married just like siblings don’t get married. And when it happens you have a bad result. It’s just not the accepted normal thing."[2] Some news sources then only mentioned the polygamy and child abuse provisions and ignored the cousin marriage portion of the bill, as did some more recent sources as well.[34][35] The new statute makes sex with an adult first cousin a more serious felony than with adult members of one's immediate family.[36]
Two US states are unusual in permitting cousin marriage with minor caveats. Maine allows first-cousin marriage if the couple agrees to have genetic counseling, while North Carolina allows it so long as the applicants for marriage are not rare double first cousins, meaning cousins through both parental lines.[37] In the other twenty-four states permitting any first-cousin marriage, double cousin marriage is also legal.[38]
[edit]Middle East
The Middle East has uniquely high rates of cousin marriage among the world's regions. Certain Middle Eastern countries, including Pakistan and Saudi Arabia, have rates of marriage to first or second cousins that may exceed 50%.[3] Iraq was estimated in one study to have a rate of 33%,[40] and figures for Iran and Afghanistan have been estimated in the range of 30-40%.[3] Though on the lower end, Egypt and Turkey nevertheless have rates above 20%.[40]
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 percent, an increase of 30 percent 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, Egypt and occupied Palestine, but increasing in Morocco, Mauritania and Sudan.[41]
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."[41]
In many Middle Eastern nations a marriage to the father's brother's daughter (FBD) is considered ideal, though this type may not always actually outnumber other types.[42]One anthropologist, Ladislav Holý, argues that it is important to distinguish between the ideal of FBD marriage and marriage as it is actually practiced, which of course often includes other types of cousins and also unrelated spouses. Holý cites the Berti people of the Sudan, who consider the FBD to be the closest kinswoman to a man outside of the prohibited range. Though they express a preference for "close" marriages, this does not mean that they necessarily prefer FBD marriage over other first cousin marriage.[43]
[edit]India
Attitudes in India on cousin marriage vary sharply by region and culture. For Muslims it is acceptable and legal to marry a first cousin. But for Hindus this is technically illegal under the Hindu Marriage Act, though the actual situation is more complex.[44]
For Hindus in northern India, cousin marriage is generally proscribed and seen as incest, as for example is the case in the state of Rajasthan. In fact it may even be undesirable to marry within one's village or for two siblings to marry partners from the same village.[45]
However, in southern India, it is common for cross cousins to marry, with matrilateral cross-cousin (mother's brother's daughter) marriages being especially favored, and this may be arranged deliberately by parents. Matrilateral cross-cousin marriage results in especially strong ties between a nephew and his maternal uncle, who is then also his father-in-law.[46]
Central India for the most part follows the northern model, though not entirely.[47]
[edit]Britain
Britain has been having a debate in the past few years 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 3% of Britain's population, of whom about 55% marry a first cousin. For example, Environment Minister (now Immigration Minister) Phil Woolas said in 2008, "If you have a child with your cousin the likelihood is there'll be a genetic problem" and that such marriages were the "elephant in the room."[48] Muslim physician Mohammad Walji has spoken out against the practice, saying that it is a "very significant" cause of infant death, and his practice has produced leaflets warning against it.[49] But in sharp contrast, Professor Alan Bittles of the Centre for Comparative Genomics in Australia states that the risk of birth defects rises from roughly 2% in the general population to 4% for first cousins and therefore that "It would be a mistake to ban it."[50]Researcher Aamra Darr of Britain's University of Leeds has also criticized what she called an "alarmist presentation of data" that exaggerates the risk.[51]
[edit]The Netherlands
The Netherlands has also had a recent debate that has reached the level of the Prime Minister proposing a cousin marriage ban. The proposed policy is explicitly aimed at preventing "import marriages" from certain nations like Turkey and Morocco with a high rate of cousin marriage (roughly one quarter according to one study). Critics argue that such a ban would contradict Section 8 of the European Convention on Human Rights, is not based on science, and would affect more than immigrants. While some proponents argue such marriages were banned until 1970, according to Frans van Poppel of the Netherlands Interdisciplinary Demographic Institute, they are confusing cousin marriage with uncle-niece marriage.[52]
[edit]Other regions
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.[53] Taiwan and North Korea also prohibit first-cousin marriage.[1]
Cousin marriage has been legally banned in China since the passage of the 1981 Marriage Law.[11] However, in practice, marriages of types besides father's brother's daughter still occur in many villages.[4] A 2002 Time article claims that an increasing imbalance in the number of males and females is causing more cousin marriages, as "desperate" males struggle to find brides.[54]
One form of cousin marriage in Ethiopia known as absuma is an arrangement made at birth. The male cousin and his family then have the right to make decisions about the girl's education and when the pair will marry.[55]
[edit]Social aspects
Robin Bennett, a University of Washington researcher who led a major NSGC study on cousin marriage, has said that much hostility towards married cousins constitutes discrimination. "It's a form of discrimination that nobody talks about. People worry about not getting health insurance — but saying that someone shouldn't marry based on how they're related, when there's no known harm, to me is a form of discrimination."[7]
A recent New York Times article by writer Sarah Kershaw documents fear by many married cousins of being treated with derision and contempt. "While many people have a story about a secret cousin crush or kiss, most Americans find the idea of cousins marrying and having children disturbing or even repulsive," notes the article. It gives the example of one mother, Mrs. Spring, whose daughter Kimberly Spring-Winters, 29, married her cousin Shane Winters, 37. She stated that when she has told people about her daughter's marriage they have been shocked, and consequently she is afraid to mention it. Living in a small Pennsylvania town, she also worries that her grandchildren will be treated as outcasts and ridiculed due to their parental status. Another cousin couple, who withheld their full names from publication, stated that their children's maternal grandparents have never met their two grandchildren because the grandparents severed contact out of disapproval for the couple's marriage.[2]
Cousin marriage is important in several anthropological theories by prominent authors such as Claude Levi-Strauss, Sir Edward Tylor, and Henry Lewis Morgan. Levi-Strauss viewed cross-cousin marriage as a form of exogamy in the context of a unilineal descent group, meaning either matrilineal or patrilineal descent. Matrilateral cross-cousin marriage in societies with matrilineal descent meant that a male married into the family his mother's brother, building an alliance between the two families. However, marriage to a mother's sister daughter (a parallel cousin) would be endogamous, here meaning inside the same descent group, and would therefore fail to build alliances between different groups. Correspondingly, in societies like China with patrilineal descent, marriage to a father's brother's daughter would fail at alliance building. And in societies with both types of descent, where a person belongs to the group of his mother's mother and father's father but not mother's father or father's mother, only cross-cousin marriages would successfully build alliances.[56]
Matrilateral cross-cousin marriage has been found by some anthropological researchers to be correlated with patripotestal jural authority, meaning rights or obligations of the father. According to some theories, in these kinship systems a man marries his matrilateral cross-cousin due to associating her with his nurturant mother. Due to this association, possibly reinforced by personal interaction with a specific cousin, he may become "fond" of her, rendering the relationship "sentimentally appropriate."[57] Interestingly, patrilateral cross-cousin marriage is the rarest of all types of cousin marriage, and there is some question as to whether it even exists.[58]
In those populations studied so far, it appears that in most societies, cousin marriage is associated with low socioeconomic status, illiteracy, and rural residence. Nevertheless, some societies also report a high prevalence among land-owning families and the ruling elite.[11]
In an essay published for The American Conservative, Steve Sailer has claimed that high rates of cousin marriage play an important role in discouraging political democracy. Sailer believes that because families practicing cousin marriage are more related to one another than otherwise, their feelings of family loyalty tend to be unusually intense, fostering nepotism.[59]
[edit]In religion
[edit]Islam
The Qur'an states that marriages between first cousins are allowed. In surat an-Nisa' (4:22-24), Allah mentioned the women who are forbidden for marriage: to quote the Qu'ran, "… Lawful to you are all beyond those mentioned, so that you may seek them with your wealth in honest wedlock…" In surat al-Ahzab (33:50), Allah mentioned to the Prophet that he may marry the daughters of his uncles and aunts from the father's side or the mother's side. It is the consensus of the jurists that this permission was not only for the Prophet, but it is also a permission for other believers. Muslims have practiced marriages between first cousins in all countries since the time of the Prophet. In many countries the most common type is between paternal cousins.[60]
The Prophet actually did marry one first cousin, Zaynab bint Jahsh, who was not only the daughter of one of his father's sisters but also was divorced from a marriage with the Prophet's adopted son, Zayd ibn Haritha. It was this last issue that caused the most controversy, with traditional Arab norms at the time being opposed, though not the Qur'an (Sura Al-Ahzab 33:37). According to Ibn Sa'd and Tabari, after Zaynab's marriage to his adopted son, the Prophet went to pay Zayd a visit, but instead found Zaynab, hastily or scantily clad, and fell in love with her. This prompted Zayd to propose divorce, but the Prophet told him to keep her. Eventually, however, Zayd did divorce her.[61][62][63]
Many of the immediate successors of Muhammad also took a cousin as one of their wives. Umar married his cousin Atikah bint Zayd ibn Amr ibn Nifayl,[64][65] while Ali married Fatimah,[66] the daughter of his paternal first cousin Muhammad and hence his first cousin once removed.[67]
[edit]Judaism and Christianity
Cousin couples existed in the Old Testament. Two of the most famous are prominent in Genesis. Isaac was married to Rebekah, his first cousin once removed (Genesis 24:12-15). Also, Rachel and Leah were both cousins of Jacob. Jacob loved Rachel and worked seven years for her father Laban in return for permission to marry (Genesis 28-29). Both marriages were arranged over significant distances, with the eligible women nearby implied to be displeasing to the groom's parents (Genesis 24:3, 28:1). Jacob's brother Esau also married his cousin Mahalath, daughter ofIshmael. According to many English Bible translations, a fourth example is the five daughters of Zelophehad, who married the "sons of their father's brothers" in the later period of Moses, although other translations merely say "relatives." (Compare the Catholic RSV-CE and NAB in Numbers 36:10-12.) Finally, the daughters of Eleazer married the sons of Eleazer's brother Kish in the still later time of David (1 Chronicles 23:22). The Bible does not define cousin marriages as right or wrong, although it does firmly prohibit sex and marriage between other closer relatives, asincest (Leviticus 18:6-18).
In Roman Catholicism, all marriages more distant than first-cousin marriages are allowed,[68] and first-cousin marriages can be contracted with a dispensation.[69] This was not always the case, however: the Catholic Church has gone through several phases in kinship prohibitions. At the dawn of Christianity in Roman times, marriages between first cousins were allowed. For example, Emperor Constantine, the first Christian Roman Emperor, married his children to the children of his half-brother. However, first and second cousin marriages were banned at the Council of Agde in AD 506. (Dispensations were sometimes granted, however.) By the 11th century, with the adoption of the so-called canon-law method of computing consanguinity, these proscriptions had been extended even to sixth cousins, including by marriage. But due to the many resulting difficulties in reckoning who was related who, they were relaxed back to third cousins at the Fourth Lateran Council in AD 1215. Pope Benedict XV reduced this to second cousins in 1917,[14] and finally, the current law was enacted in 1983.[69] In Catholicism, close relatives who have married unwittingly without a dispensation can receive an annulment.
There are several explanations for the rise of Catholic cousin marriage prohibitions after the fall of Rome. One explanation is increasing Germanic influence on church policy. G.E. Howard states, "During the period preceding the Teutonic invasion, speaking broadly, the church adhered to Roman law and custom; thereafter those of the Germans...were accepted."[70] On the other hand it has also been argued that the bans were a reaction against local Germanic customs of kindred marriage.[71] At least one Frankish King, Pepin the Short, apparently viewed close kin marriages among nobles as a threat to his power.[72] Whatever the reasons, written justifications for such bans had been advanced by St. Augustine by the fifth century. "It is very reasonable and just," he wrote, "that one man should not himself sustain many relationships, but that various relationships should be distributed among several, and thus serve to bind together the greatest number in the same social interests."[5] Taking a contrary view, Protestants writing after the Reformation tended to see the prohibitions and the dispensations needed to circumvent them as part of an undesirable church scheme to accrue wealth, or "lucre."[5]
Since the 13th century the Catholic Church has measured consanguinity according to what is called, perhaps confusingly, the civil-law method. Under this method, the degree of relationship between lineal relatives (i.e., a man and his grandfather) is simply equal to the number of generations between them. However, the degree of relationship between collateral (non-lineal) relatives equals the number of links in the family tree from one person, up to the common ancestor, and then back to the other person. Thus brothers are related in the second degree, and first cousins in the fourth degree.[73]
Protestant churches generally allow cousin marriage,[74] following the early pronouncements of Martin Luther and John Calvin during the Reformation.[13] This includes most of the major US denominations such as Baptist, Pentecostal, Lutheran, Presbyterian, and Methodist. The Anglican Communion has also allowed cousin marriage since the time of King Henry VIII. Protestants during the Reformation struggled to interpret the Biblical proscriptions against incest in a sensible manner, a task frustrated by facts like their omission of the daughter (but inclusion of the granddaughter) as a prohibited relation.[5] John Calvin thought of the Biblical list only as illustrative and that any relationship of the same or smaller degree as any listed, namely the third degree by the civil-law method, should therefore be prohibited. The Archbishop of Canterbury reached the same conclusion soon after.[14] But in contrast to both Protestantism and Catholicism, the Eastern Orthodox Church bars up to second cousins from marrying.[11]
The 1913 Catholic Encyclopedia refers to a theory by the Anglican bishop of Bath and Wells speculating that Mary and Joseph, the mother of Jesus and her husband, were first cousins.[75] However, this is neither stated in the Bible nor officially accepted by any major church.
[edit]Hinduism
In the Mahabharata, one of the two great Hindu Epics, Arjuna took as his fourth wife his first and cross cousin Subhadra, the sister of Krishna. Arjuna had gone into exile alone after having disturbed Draupadi and Yudhisthira in their private quarters. It was during the last part of his exile, while staying at the Dvaraka residence of his cousins, that he fell in love with Subhadra.
According to Chapter 86 of the Krsna Book, while eating at the home of Balaramaji, Arjuna noticed the beautiful Subhadra, who was very enchanting even to the great heroes and kings. Out of love for her, Arjuna's eyes brightened, and he began to see her with glittering eyes. Arjuna decided that somehow or other he would achieve Subhadra as his wife, and his mind became agitated on account of this desire.
Once married, Subhadra and Arjuna had a son, Abhimanyu. Later, Abhimanyu and his wife Uttara had a son, Parikshit, who became the sole surviving member of the entire Kuru dynasty after Abhimanyu was killed at Kurukshetra. Parikshit then succeeded Yudhisthira as the emperor of the Pandava kingdom.[76]
[edit]Other religions
Buddhism does not proscribe any specific sexual practices, only ruling out "sexual misconduct" as part of the Five Precepts.[77] Zoroastrianism allows cousin marriages, but Sikhism does not.[11]
[edit]Biological aspects
[edit]Genetics
Cousin marriage has genetic aspects that do not arise in the case of other marriage-related political and social issues like interracial marriage. This is because married couples possessing higher than normal consanguinity have, on average, an increased chance of sharing genes for recessive traits. Consanguinity means the amount of shared (identical) DNA, the genetic material. The percentage ofconsanguinity between any two individuals decreases fourfold as the most recent common ancestor recedes one generation. To cite some examples, first cousins have four times the consanguinity of second cousins, and first cousins once removed have half the shared DNA as full first cousins. Comparatively rare double first cousins share twice the consanguinity as first cousins and are as related as half-siblings.
In April 2002, the Journal of Genetic Counseling released a report which showed that the potential risk of birth defects in a child born of first cousins was slightly higher than the risk associated with a non-cousin couple. The report estimated the increased risk for first cousins at 1.7-2.8% over the base risk of about 3%, or about the same as that of any woman over age 40.[78] Also, a 1994 study found a mean excess pre-reproductive mortality rate of 4.4%,[79] while another study published in 2009 suggests the rate may be closer to 3.5%.[2] 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.[80] Critics argue that banning first-cousin marriages would make as much sense as trying to ban childbearing by older women. These numbers were reported only for first instances of cousin mating; repeated generations of cousin marriage can increase this risk, especially if the original ancestors were carriers of deleterious recessive genes, resulting in a founder effect.[81]
A BBC report[82] discussed Pakistanis in Britain, 55% of whom marry a first cousin. Given the high rate of such marriages, many children come from repeat generations of first-cousin marriages. The report states that these children are 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 dies in infancy or develops a serious disability. The BBC also states that Pakistani-Britons, who account for some 3% of all births in the UK, produce "just under a third" of all British children with genetic illnesses.
However, according to a statement by the UK's Human Genetics Commission on cousin marriages, the BBC "fails to clarify" that children born to these marriages are not 13 times more likely to develop genetic disorders. Rather, they are 13 times more likely to develop recessive genetic disorders. The HGC states, "Other types of genetic conditions, including chromosomal abnormalities, sex-linked conditions and autosomal dominant conditions are not influenced by cousin marriage." The HGC goes on to compare the biological risk between cousin marriage and increased maternal age, arguing that "Both represent complex cultural trends. Both however, also carry a biological risk. They key difference, GIG argue, is that cousin marriage is more common amongst a British minority population."[83]
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 understandably against the practice.
The Human Genetics Commission recommends comparing the strategy taken in dealing with cousin marriage to previous strategies on increased maternal age, notably as this age relates to an increased risk of Down Syndrome. In the UK's system of socialized medicine, all pregnant women are offered a screening test to identify those at an increased risk of having a baby with this syndrome. The HGC states that similarly, "it is appropriate to offer genetic counseling to couples whose relationship is consanguineous, preferably before they conceive, in order to establish the precise risk of a genetic abnormality in their children." Under this position the offering of genetic counseling can be refused, unlike for example in the US state of Maine where it is mandatory to obtain a marriage license.
[edit]Fertility
In general, higher total fertility rates are reported for cousin marriages than average, a phenomenon noted as far back as George Darwin during the late 19th century. This may be partly explained by the lower average parental age at marriage, and age at first birth, observed in these cases. Other factors include shorter birth intervals and possibly a lower likelihood of using reliable contraception.[11] At least according to one paper, it does not appear that the fertility difference is due to any underlying biological effect caused by consanguinity.[84]
[edit]Famous cousin marriages
Famous cousin marriages in the United States include Edgar Allen Poe, Albert Einstein, Franklin Delano Roosevelt, and Jerry Lee Lewis.[
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