Endogamy is the cultural practice of mating within a specific social group, religious denomination, caste, or ethnic group, rejecting any from outside of the group or belief structure as unsuitable for marriage or other close personal relationships. Its opposite, exogamy, describes the social norm of marriage outside of the group.
Endogamy is common in many cultures and ethnic groups. Several religious and ethnic religious groups are traditionally more endogamous, although sometimes mating outside of the group occurs with the added dimension of requiring marital religious conversion. This permits an exogamous marriage, as the convert, by accepting the partner's religion, becomes accepted within the endogamous group. Endogamy may result in a higher rate of recessive gene-linked genetic disorders.
Endogamy can encourage sectarianism and serves as a form of self-segregation. For instance, a community resists integration or completely merging with the surrounding population. Minorities can use it to stay ethnically homogeneous over a long time as distinct communities within societies that have other practices and beliefs.
The isolationist practices of endogamy may lead to a group's extinction, as genetic diseases may develop that can affect an increasing percentage of the population. However, this disease effect would tend to be small unless there is a high degree of close inbreeding, or if the endogamous population becomes very small in size.
The Urapmin, a small tribe in Papua New Guinea, practice strict endogamy. The Urapmin also have a system of kinship classes known as tanum miit. Since the classes are inherited cognatically, most Urapmin belong to all of the major classes, creating great fluidity and doing little to differentiate individuals.[1]
The small community on the South Atlantic island of Tristan da Cunha are, because of their geographical isolation, an almost endogamic society. There are instances of health problems attributed to endogamy on the island, including glaucoma and asthma as research by the University of Toronto has demonstrated.[2]
Endogamic marriage patterns may increase the frequency of various levels of cousin marriage in a population, and may cause high probability of children of first, second, third cousins, etcetera.
If a cousin marriage has accrued in a known ancestral tree of a person, in historical time, it is referred to as pedigree collapse. This may cause relations along multiple paths between a person's autosomal-DNA matches. It creates stronger DNA matches between the DNA matches than expected from the nearest path.[3]
Cousin marriage should not be confused with double cousins, which do not cause a pedigree collapse. Certain levels of sibling marriage and cousin marriage is prevented by law in some countries, and referred to as consanguinity.
A long term pattern of endogamy in a region may increase the risk of repeated cousin marriage during a long period of time, referred to as inbreeding. It may cause additional noise in the DNA autosomal data, giving the impressions that DNA matches with roots in that region are more closely related than they are.
Lepcha, an ethnic group in India, Nepal, and Bhutan
Judaism traditionally mandates religious endogamy, requiring that both marriage partners be Jewish, while allowing for marriage to converts. Orthodox Judaism maintains the traditional requirement for endogamy in Judaism as a binding,[13] inherent part of Judaism's religious beliefs and traditions.[14]
The Knanaya, an endogamous group within the St. Thomas Christian Community of India. The community claims to have arrived to India in the fourth century and have been noted for their historical practice of endogamy.[citation needed]
The Surti and the Kaanam (Bharuchis) of Gujarat. In Gujarat on either side of the Narmada River lies two major cities, Surat and Bharuch. Those lying south of Narmada are generally termed as Surtis and those north of it are termed as Kaanam. Endogamy was historically practiced amongst these two groups and it continued as they migrated to other regions of the world. Surtis would only marry Surtis and Kaanams would only marry Kaanams. It is only recently in the past 50 years that this practice has been discontinued. Before that, if a girl's family could not find a suitable partner amongst their group in the migrated land, they would prefer getting her married to a boy from back home (Gujarat) even though boys of marriageable age would be available in their land of migration.
^Robbins, Joel (2004). Becoming Sinners: Christianity and Moral Torment in a Papua New Guinea Society. University of California Press. pp. 191–192. ISBN0-520-23800-1.
^David Reich (2019), Who We Are and How We Got Here: Ancient DNA and the New Science of the Human PastISBN978-019-882-1250, pages 219-223. Quote: "Today there is an intricate caste system that shapes the lives of many people within Ethiopia, with elaborate rules preventing marriage between groups with different traditional roles. The Ari include three subgroups--the Cultivators, Blacksmiths, and Potters--who are socially and genetically differentiated from one another and from non-Ari groups. Since the Ari have a distinctive genetic affinity to the forty-five-hundred-year-old ancient highland individual compared to other Ethiopian groups, it is clear that there were strong local barriers to gene exchange and homogenization within the region of present-day Ethiopia that persisted for at least forty-five hundred years. This is the best example of strong endogamy that I know of even more ancient than the evidence of endogamy in India that so far is only documented as going back a couple of thousand
years."
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