Bans against consanguinity have been around for thousands, of years, though they differ by degree and culture. The Greeks had no single name for it, a similar term not appearing until around the 9th century—for instance, classic Athenian law stated that children of the same father could marry—i.e., a half-brother and half-sister (Ager, 2005). But what were some of the original reasons why they were banned—eugenic considerations or cultural/closeness reasons? Why were people banned from having a partner that was too close to them? Throughout history, different cultures obviously had different practices. The Roman Catholic Church, Pharaonic and Ptolemic Egypt, ancient Iran, all had different practices, for different reasons, on close marriage to relatives. The ban on first-cousin marriage appeared in American law around the time of the Civil War—clearly, then, the cousin-marriage ban in America was not based on the eugenics movement, though it was eugenic in nature (Paul and Spencer, 2008). Though there was debate on the matter during the Progressive Era (Wilson).
Schneider addressed sexual and matrimonial prohibitions among the Yapese in an early article (1957), but he developed his approach in a volume devoted to the subject of incest (1976). It was in the latter that he presented his culturalist views on the topic, making the important point that ‘the most frequent confusion found in the literature in my experience is the confusion between the question of the origin of the prohibition on incest and the question of why it is maintained long after the conditions which may account for its origin have passed’(Schneider 1976: 156). He went on to argue that ‘the incest prohibition is not universal’, supporting this affirmation with the cases of brother–sister marriages of Pharaonic and Ptolemaic Egypt, the ‘apparent lack’ of an incest prohibition in ancient Iran, and the marriages between members of the royal family of Hawaii as analysed by Marshall Sahlins (Schneider 1976: 154). None of these relations would be considered as incestuous for the native people. He also insisted on the inclusion of kin other than nuclear kin in the different prohibitions that Europeans identify as incestuous, on the importance of elements such as food for determining who a person can and cannot have sexual relations with and on cases in which incest includes non-sexual behaviour. He then proposed equating incest with the idea of acting ‘ungrammatically’ in a given cultural code (Schneider 1976: 167). Thus, for Schneider, a priori deﬁnitions of incest based on a Western tendency to relate kinship to sexual intercourse and the birth of a child should be avoided. Rather, he argued, we should adopt a cultural and symbolic approach towards each case. [See also Scheidel, 1997 for more information on sibling and half-sibling marriage in Roman Egypt. They did this to keep the throne in the family; Galton, 1998]
But the Romans were the first to dissuade consanguineous marriages when Emperor Claudius married his niece Agrippina in the middle of the 1st century. Then, in the middle of the fifth century, which the Roman Catholic Church eventually picked up, with the Pope citing passages in Leviticus to justify the banning of marriages with close kin (Bittles, 2009). (I should bring up the ‘Hajnal line’ now, but I’ll save that for an article by itself. In the meantime, read Steinbach, Kuhnt, and Knull, 2016 where they show that by taking marriage rate, divorce rate, step-families, and single-parent prevalence into account, we cannot use the ‘Hajnal line’ to explain differences between East and West Europe”; see also who argue that Szolyysek and Ogorek, 2019 who show that when regional populations cluster on familial traits that they lie outside of the ‘line’, which calls into questions the conclusions of Hajnal and his acolytes.)
When it comes to these cases, the ban on close marriages was not to have healthy children—and therefore attempt to prevent the types of problems that arise through the marriage of a close relative if they conceive a child—the ban was to avoid relationships that lacked difference on a bio-social level. One example here would be in certain Muslim communities. Children who shared the same wet nurse—a nurse who breastfeeds for parents—were banned from having any kind of relations later in life as they were known as ‘milk-siblings’:
Children who have been regularly breastfed (three to five or more times) by the same woman are considered “milk-siblings” and are prohibited from marrying each other. It is forbidden for a man to marry his milk mother (wet nurse) or for a woman to marry her milk mother’s husband.
In Leviticus 18:6-18, Deuteronomy 22:30, and Deuteronomy 27:2-23 the authors spake against marriage with close (blood) relatives while in Leviticus 20:11-21 along with the prohibitions against relations with blood kin, even your uncle’s wife was out of the question (the unrelated wife). When it comes to the Roman Catholic Church banning cousin marriage, however, there is a debate as to what the impetus for the ban was: was it due to eugenic considerations or to ban the marriage of two close individuals, no matter their relatedness status? MacKellar and Bechtel (2014: 62) write:
It is likely, however, that the basis for this prohibition on consanguinity [in the Roman Catholic Church] was not a concern for eugenic considerations. The condemnation of affinity, such as marrying a step-daughter (cannon 1092) and marrying an adopted child or sibling (cannon 1094) implies that these codes were again drafted on the basis of avoiding sexual relationships between people who were considered too similar or who had something ‘overly in common.’
Parkes (2005) notes that even marriage between a godparent and godchild was banned in Christian communities. I grew up Roman Catholic and I, too, would not marry my Godmother (who is my fourth cousin). MacKellar and Bechtel (2014: 63) do note that the Christian Church even banned relationships between, say, student and teacher to prevent “sexual corruption and abuse. These sexual restrictions were not, therefore, drafted to protect progeny from inheritable disorders but were similar to those that prevent relationships between teachers and their pupils or doctors with their patients. These relationships were prohibited even though it may have been certain that no child would ever be born.
Chinese cousin marriage prohibitions are interesting. First cousins could marry eac other if they did not have the same surname but if they had the same surname they were barred from marriage, as Wong (2017) notes that “The old Chinese system is a patriarchal system, where children take the surname of the father. In this patriarchal system, first cousins of the same surname could not marry. First cousins, with different surnames, could marry.”
Many Asian ethnies have the same or similar surnames. So, on that basis, it is interesting to note that in Korea, for example, much cultural shame is brought on people who choose to marry and have the same last name. It is so taboo that family and friends question their loved ones who date a person with their same last name. The New York Times has an interesting story from the mid-90s about Koreans and dating/marrying an individual with the same last name:
It should be a time of celebration. K. H. Lee and his girlfriend have fallen in love and want to get married soon to start a new life together.
But Mr. Lee, a 31-year-old civil servant, and his fiancee face a battle against Korean history that threatens to bring their love to ruin: they have the same last name. Even his friends disapprove of his plans.
“I can feel them asking, ‘Do you really have to do this?'” said Mr. Lee, who, who would not disclose his full given name or his girlfriend’s because the issue is so delicate. “Even if it were allowed by law, if the relatives found out, the whole family would be shamed because we have a strong sense of face.” Not being able to marry a person with the same family name is a special burden in South Korea, where 22 percent of South Korea’s 44 million people are named Kim. The figure leaps to 55 percent after adding in Park, Lee, Choi, and Chong.
The NYT story also notes an interesting bit of Korean folklore about this ban:
According to folklore, the practice was brought over from China in the 14th century, after a Korean messenger, named Lee, visited China. His Chinese host asked him his wife’s name, and upon hearing that it was also Lee, the Chinese supposedly replied: “Ah! You’re not an aristocrat. You’re a commoner!” When the messenger returned, he relayed the story to the Korean emperor, who immediately declared a ban against same-clan marriages.
Dating people with the same last name in South Korea is such a taboo that some people even attempt to find out their perspective SO’s last name discretely. The practice, to them is cultural as of now since presumably, marriage and children with one with the same last name won’t lead to any birth defects.
We have been marrying/conceiving children with close relatives since time immemorial. Though, different peoples have different reasons for shunning consanguineous marriages—some cultural, some biological, some both. The Greeks banned it in some instances, but allowed it in others. In Islam, children who are “milk-siblings” cannot marry. Asians (who are likely to share names with their own ethny, and even sometimes another Asian of a different ethny) have some interesting considerations on cousin marriages—it being so engrained in their culture that some will not talk to someone if they share their last name. The considerations of banning consanguineous marriages by the Church, though, could go both ways—it could be due to banning marriages between people who are ‘related’ socially, and not genetically.
The history of cousin marriage—along with the banning/allowing it throughout history, along with how different peoples handle the situation shows exactly how humans individuate through culture.