Exogamy

Exogamy is the social norm of mating or marrying outside one's social group. The group defines the scope and extent of exogamy, and the rules and enforcement mechanisms that ensure its continuity. One form of exogamy is dual exogamy, in which two groups continually intermarry with each other.^[1]

In social science, exogamy is viewed as a combination of two related aspects: biological and cultural. Biological exogamy is the marriage of people who are not blood relatives. This is regulated by incest taboos and laws against incest. Cultural exogamy is marrying outside a specific cultural group; the opposite being endogamy, marriage within a social group.

Biology of exogamy

Exogamy often results in two individuals that are not closely genetically related marrying each other; that is, outbreeding as opposed to inbreeding. In moderation, this benefits the offspring as it reduces the risk of the offspring inheriting two copies of a defective gene. Increasing the genetic diversity of the offspring improves the chances of offspring reproducing, up until the fourth-cousin level of relatedness; however, reproduction between individuals on the fourth-cousin level of relatedness decreases evolutionary fitness.^[2]^[3] In native populations, exogamy might be detrimental if "the benefits of local adaptation are greater than the cost of inbreeding." However, non-native, "invasive" populations that have "not yet established a pattern of local adaptation" may derive some adaptive benefit from admixture.^[4]

Nancy Wilmsen Thornhill states that the drive in humans to not reproduce or be attracted to one's immediate family is evolutionarily adaptive, as it reduces the risk of children having genetic defects caused by inbreeding, as a result of inheriting two copies of a deleterious recessive gene.^[5]

In one Old Order Amish society, inbreeding increases the risk of "neonatal and postneonatal mortality."^[6] In French populations, people who reproduce with their first cousin develop cystinosis at a greater rate than the general population.^[7]

Cultural exogamy

Cultural exogamy is the custom of marrying outside a specified group of people to which a person belongs. Thus, persons may be expected to marry outside their totem clan(s) or other groups, in addition to outside closer blood relatives.

Researchers have proposed different theories to account for the origin of exogamy. Edvard Westermarck said an aversion to marriage between blood relatives or near kin emerged with a parental deterrence of incest. From a genetic point of view, aversion to breeding with close relatives results in fewer congenital diseases. If one person has a faulty gene, breeding outside his group increases the chances that his partner will have another functional type gene and their child may not suffer the defect. Outbreeding favours the condition of heterozygosity, that is having two nonidentical copies of a given gene. J. F. McLennan^[8] holds that exogamy was due originally to a scarcity of women among small bands. Men were obliged to seek wives from other groups, including marriage by capture, and exogamy developed as a cultural custom.

Émile Durkheim^[9] derives exogamy from totemism. He said that a people had religious respect for the blood of a totemic clan, for the clan totem is a god and is present especially in the blood, a sacred substance.

In some forms of Hinduism such as Shaktism, people can only marry outside their gotra which is a traditional group of people who may be distantly related but have been living in the same area or have an ancestral home in the same area.

Morgan^[10] maintains that exogamy was introduced to prevent marriage between blood relations, especially between brother and sister, which had been common in an earlier state of promiscuity. Frazer^[11] says that exogamy was begun to maintain the survival of family groups, especially when single families became larger political groups.

Claude Lévi-Strauss introduced the "Alliance Theory" of exogamy,^[12] that is, that small groups must force their members to marry outside so as to build alliances with other groups. According to this theory, groups that engaged in exogamy would flourish, while those that did not would all die, either literally or because they lacked sufficient ties for cultural and economic exchange, leaving them at a disadvantage. The exchange of men or women served as a uniting force between groups.

Dual exogamy

Dual exogamy is a traditional form of arranging marriages in numerous modern societies and in many societies described in classical literature. It can be matrilineal or patrilineal. It is practiced by some Australian tribes,^[13] historically widespread in the Turkic societies,^[14]^[15] Taï societies (Ivory Coast),^[16] Eskimo,^[17] among Ob-Ugrians^[18]^[19] and others. In tribal societies, the dual exogamy union lasted for many generations, ultimately uniting the groups initially unrelated by blood or language into a single tribe or nation.

Linguistic exogamy

Linguistic exogamy is a form of cultural exogamy in which marriage occurs only between speakers of different languages. The custom is common among indigenous groups in the northwest Amazon, such as the Tucano tribes.^[20]

References

^ New Zealand Slavonic Journal, Victoria University of Wellington, 2002, Volumes 35-36, p.81 OCLC 297663912
^ Helgason A, Pálsson S, Gudbjartsson DF, Kristjánsson T, Stefánsson K (February 2008). "An association between the kinship and fertility of human couples". Science. 319 (5864): 813–6. Bibcode:2008Sci...319..813H. doi:10.1126/science.1150232. PMID 18258915. S2CID 17831162.
^ Labouriau R, Amorim A (December 2008). "Comment on "An association between the kinship and fertility of human couples"". Science. 322 (5908): 1634, author reply 1634. Bibcode:2008Sci...322.1634L. doi:10.1126/science.1161907. PMID 19074330.
^ Verhoeven KJ, Macel M, Wolfe LM, Biere A (January 2011). "Population admixture, biological invasions and the balance between local adaptation and inbreeding depression". Proceedings. Biological Sciences. 278 (1702): 2–8. doi:10.1098/rspb.2010.1272. PMC 2992731. PMID 20685700.
^ Thornhill N (1993). The Natural History of Inbreeding and Outbreeding: Theoretical and Empirical Perspectives. Chicago: The University of Chicago Press.
^ Dorsten LE, Hotchkiss L, King TM (May 1999). "The effect of inbreeding on early childhood mortality: twelve generations of an Amish settlement". Demography. 36 (2): 263–71. doi:10.2307/2648113. JSTOR 2648113. PMID 10332616. S2CID 26311145.
^ Tchen P, Bois E, Feingold J, Feingold N, Kaplan J (September 1977). "Inbreeding in recessive diseases". Human Genetics. 38 (2): 163–7. doi:10.1007/BF00527398. PMID 302820. S2CID 8849012.
^ McLennan JF (1888). "The Origin of Exogamy". The English Historical Review. 3 (9): 94–104. doi:10.1093/ehr/iii.ix.94.
^ Fraser JG (1910). Totemism and Exogamy Vol. IV. New York: Cosimo Inc. pp. 100–102. ISBN 9781605209814.
^ Morgan LH (1871). "Systems of Consanguinity and Affinity of the Human Family". Smithsonian Contributions to Knowledge. 41 (2). Smithsonian Institution.
^ Frazer JG (1910). Totemism and Exogamy Vol. IV. New York: Cosimo Inc. p. 95. ISBN 9781605209791.
^ "Alliance Theory". Encyclopædia Britannica. Retrieved 15 March 2012.
^ Bose JK (1980). Glimpses of Tribal Life in North-east India. Calcutta. p. 52.{{cite book}}: CS1 maint: location missing publisher (link)
^ Turkish Studies Association Bulletin, 1982, Volume 6, p.79
^ Potapov LP (1969). "Ethnic Composition and Origin of Altaians". Science. Leningrad: 44.
^ Effects of the growth of human activities on the Taï forest of the south-west of the Ivory coast (PDF). UNESCO. December 2017.^{[permanent dead link]}
^ Fainberg L (1967). "On the Question of the Eskimo kinship system". Arctic Anthropology. 4 (1): 244.
^ Golovnev AV. "From One to Seven: Numerical Symbolism in Khanty Culture". Arctic Anthropology. 31 (1): 62–71.
^ Csepregi, Márta (2009). "The very highly connected nodes in the Ob-Ugrian networks" (PDF). Suomalais-Ugrilaisen Seuran Toimituksia = Mémoires de la Société Finno-Ougrienne. 258: 15.
^ Jackson JE (1983). The Fish People - Linguistic Exogamy and Tukanoan Identity in Northwest Amazonia. Cambridge University Press.