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Incest ( ) is
sex Sex is the biological trait that determines whether a sexually reproducing organism produces male or female gametes. During sexual reproduction, a male and a female gamete fuse to form a zygote, which develops into an offspring that inheri ...
between close relatives, for example a
brother A brother (: brothers or brethren) is a man or boy who shares one or more parents with another; a male sibling. The female counterpart is a sister. Although the term typically refers to a family, familial relationship, it is sometimes used ende ...
,
sister A sister is a woman or a girl who shares parents or a parent with another individual; a female sibling. The male counterpart is a brother. Although the term typically refers to a familial relationship, it is sometimes used endearingly to ref ...
, or
parent A parent is either the progenitor of a child or, in humans, it can refer to a caregiver or legal guardian, generally called an adoptive parent or step-parent. Parents who are progenitors are First-degree relative, first-degree relatives and have ...
. This typically includes sexual activity between people in
consanguinity Consanguinity (from Latin '':wikt: consanguinitas, consanguinitas'' 'blood relationship') is the characteristic of having a kinship with a relative who is descended from a common ancestor. Many jurisdictions have laws prohibiting people who are ...
(blood relations), and sometimes those related by lineage. It is condemned and considered immoral in many societies. It can lead to an increased risk of
genetic disorders A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosome abnormality. Although polygenic disorders are ...
in children in case of pregnancy from incestuous sex. The
incest taboo Incest ( ) is sex between close relatives, for example a brother, sister, or parent. This typically includes sexual activity between people in consanguinity (blood relations), and sometimes those related by lineage. It is condemned and con ...
is one of the most widespread of all cultural
taboo A taboo is a social group's ban, prohibition or avoidance of something (usually an utterance or behavior) based on the group's sense that it is excessively repulsive, offensive, sacred or allowed only for certain people.''Encyclopædia Britannica ...
s, both in present and in past societies. Most modern societies have
laws regarding incest Laws regarding incest (i.e. sexual activity between family members or close relatives) vary considerably between jurisdictions, and depend on the type of sexual activity and the nature of the family relationship of the parties involved, as well ...
or social restrictions on closely consanguineous marriages. In societies where it is illegal, consensual adult incest is seen by some as a
victimless crime A victimless crime is an illegal act that typically either directly involves only the perpetrator or occurs between consenting adults. Because it is consensual in nature, whether there involves a victim is a matter of debate. Definitions of vi ...
. Some cultures extend the incest taboo to relatives with no consanguinity, such as milk-siblings, stepsiblings, and adoptive siblings, albeit sometimes with less intensity. Third-degree relatives (such as half-aunt, half-nephew, first cousin) on average have 12.5% common genetic heritage, and sexual relations between them are viewed differently in various cultures, from being discouraged to being socially acceptable. Children of incestuous relationships have been regarded as
illegitimate Legitimacy, in traditional Western common law, is the status of a child born to parents who are legally married to each other, and of a child conceived before the parents obtain a legal divorce. Conversely, ''illegitimacy'', also known as ''b ...
, and are still so regarded in some societies today. In most cases, the parents did not have the option to marry to remove that status, as incestuous marriages were, and are, normally also prohibited. A common justification for prohibiting incest is avoiding
inbreeding Inbreeding is the production of offspring from the mating or breeding of individuals or organisms that are closely genetic distance, related genetically. By analogy, the term is used in human reproduction, but more commonly refers to the genet ...
, a collection of
genetic disorders A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosome abnormality. Although polygenic disorders are ...
suffered by the children of parents with a close genetic relationship. Such children are at greater risk of congenital disorders, developmental and physical disability, and death; that risk is proportional to their parents'
coefficient of relationship The coefficient of relationship is a measure of the degree of consanguinity (or biological relationship) between two individuals. The term coefficient of relationship was defined by Sewall Wright in 1922, and was derived from his definition of th ...
, a measure of how closely the parents are related genetically. However, cultural anthropologists have noted that
inbreeding avoidance Inbreeding avoidance, or the inbreeding avoidance hypothesis, is a concept in evolutionary biology that refers to the prevention of the harmful effects of inbreeding. The inbreeding avoidance hypothesis posits that certain mechanisms develop with ...
cannot form the sole basis for the incest taboo because the boundaries of the incest prohibition vary widely between cultures and not necessarily in ways that maximize the avoidance of inbreeding. In some societies, such as those of
Ancient Egypt Ancient Egypt () was a cradle of civilization concentrated along the lower reaches of the Nile River in Northeast Africa. It emerged from prehistoric Egypt around 3150BC (according to conventional Egyptian chronology), when Upper and Lower E ...
, brother-sister, father-daughter, mother-son, cousin-cousin, aunt-nephew, uncle-niece, and other combinations of relations within a
royal family A royal family is the immediate family of monarchs and sometimes their extended family. The term imperial family appropriately describes the family of an emperor or empress, and the term papal family describes the family of a pope, while th ...
were married as a means of perpetuating the royal lineage. Some societies have different views about what constitutes illegal or immoral incest. For example, in
Samoa Samoa, officially the Independent State of Samoa and known until 1997 as Western Samoa, is an island country in Polynesia, part of Oceania, in the South Pacific Ocean. It consists of two main islands (Savai'i and Upolu), two smaller, inhabited ...
, a man was permitted to marry his older sister, but not his younger sister. However, sexual relations with a first-degree relative (meaning a parent, sibling, or child) were almost universally forbidden.


Terminology

The English word ''
incest Incest ( ) is sexual intercourse, sex between kinship, close relatives, for example a brother, sister, or parent. This typically includes sexual activity between people in consanguinity (blood relations), and sometimes those related by lineag ...
'' is derived from the Latin ''incestus'', which has a general meaning of "impure, unchaste". It was introduced into
Middle English Middle English (abbreviated to ME) is a form of the English language that was spoken after the Norman Conquest of 1066, until the late 15th century. The English language underwent distinct variations and developments following the Old English pe ...
, both in the generic Latin sense (preserved throughout the Middle English period) and in the narrow modern sense. The derived adjective ''incestuous'' appears in the 16th century. Before the Latin term came in, incest was known in
Old English Old English ( or , or ), or Anglo-Saxon, is the earliest recorded form of the English language, spoken in England and southern and eastern Scotland in the Early Middle Ages. It developed from the languages brought to Great Britain by Anglo-S ...
as ''sib-leger'' (from ''sibb'' 'kinship' + ''leger'' 'to lie') or ''mǣġhǣmed'' (from ''mǣġ'' 'kin, parent' + ''hǣmed'' 'sexual intercourse') but in time, both words fell out of use. Terms like ''incester'' and ''incestual'' have been used to describe those interested or involved in sexual relations with relatives among humans, while ''inbreeder'' has been used in relation to similar behavior among non-human organisms.


History


Antiquity

In
ancient China The history of China spans several millennia across a wide geographical area. Each region now considered part of the Chinese world has experienced periods of unity, fracture, prosperity, and strife. Chinese civilization first emerged in the Y ...
, first cousins with the same surnames (i.e. those born to the father's brothers) were not permitted to marry, while those with different surnames could marry (i.e. maternal cousins and paternal cousins born to the father's sisters). In
Achaemenid Persia The Achaemenid Empire or Achaemenian Empire, also known as the Persian Empire or First Persian Empire (; , , ), was an Iranian empire founded by Cyrus the Great of the Achaemenid dynasty in 550 BC. Based in modern-day Iran, it was the larges ...
, marriages between family members, such as half-siblings, nieces and cousins took place but were not seen as incestuous. However, Greek sources state that brother-sister and father-daughter marriages allegedly took place inside the royal family, yet it remains problematic to determine the reliability of these accounts. According to
Herodotus Herodotus (; BC) was a Greek historian and geographer from the Greek city of Halicarnassus (now Bodrum, Turkey), under Persian control in the 5th century BC, and a later citizen of Thurii in modern Calabria, Italy. He wrote the '' Histori ...
, Shah
Cambyses II Cambyses II () was the second King of Kings of the Achaemenid Empire, reigning 530 to 522 BCE. He was the son of and successor to Cyrus the Great (); his mother was Cassandane. His relatively brief reign was marked by his conquests in North Afric ...
supposedly married two of his sisters,
Atossa Atossa (Old Persian: ''Utauθa'', or Old Iranian: ''Hutauθa''; 550–475 BC) was an Achaemenid empress. She was the daughter of Cyrus the Great, the sister of Cambyses II, the wife of Darius the Great, the mother of Xerxes the Great and the gr ...
and Roxane. This would have been regarded as illegal. However, Herodotus also states that Cambyses married Otanes' daughter Phaidyme, whilst his contemporary
Ctesias Ctesias ( ; ; ), also known as Ctesias of Cnidus, was a Greek physician and historian from the town of Cnidus in Caria, then part of the Achaemenid Empire. Historical events Ctesias, who lived in the fifth century BC, was physician to the Acha ...
names Roxane as Cambyses' wife, but she is not referred to as his sister. The accusations against Cambyses of committing incest are mentioned as part of his "blasphemous actions", which were designed to illustrate his "madness and vanity". These reports all derive from the same Egyptian source that was antagonistic towards Cambyses, and some of these allegations of "crimes", such as the killing of the Apis bull, have been confirmed as false, which means that the report of Cambyses' supposed incestuous acts is questionable. Several of the Egyptian
king King is a royal title given to a male monarch. A king is an Absolute monarchy, absolute monarch if he holds unrestricted Government, governmental power or exercises full sovereignty over a nation. Conversely, he is a Constitutional monarchy, ...
s married their sisters and had several children with them to continue the royal bloodline. For example,
Tutankhamun Tutankhamun or Tutankhamen, (; ), was an Egyptian pharaoh who ruled during the late Eighteenth Dynasty of Egypt, Eighteenth Dynasty of ancient Egypt. Born Tutankhaten, he instituted the restoration of the traditional polytheistic form of an ...
married his half-sister
Ankhesenamun Ankhesenamun (, "Her Life Is of Amun"; c. 1348 or c. 1342 – after 1322 BC) was an ancient Egyptian queen who lived during the Eighteenth Dynasty of Egypt, 18th Dynasty of Egypt. Born Ankhesenpaaten (, "she lives for the Aten"), she was the ...
, and was himself the child of an incestuous union between
Akhenaten Akhenaten (pronounced ), also spelled Akhenaton or Echnaton ( ''ʾŪḫə-nə-yātəy'', , meaning 'Effective for the Aten'), was an ancient Egyptian pharaoh reigning or 1351–1334 BC, the tenth ruler of the Eighteenth Dynasty of Egypt, Eig ...
and an unidentified sister-wife. Several scholars, such as Frier et al., state that sibling marriages were widespread among all classes in Egypt during the Graeco-Roman period. Numerous
papyri Papyrus ( ) is a material similar to thick paper that was used in ancient times as a writing surface. It was made from the pith of the papyrus plant, ''Cyperus papyrus'', a wetland sedge. ''Papyrus'' (plural: ''papyri'' or ''papyruses'') can ...
and the Roman census declarations attest to many husbands and wives being brother and sister, of the same father and mother. However, it has also been argued that the available evidence does not support the view that such relations were common. The most famous of these relationships were in the Ptolemaic royal family;
Cleopatra VII Cleopatra VII Thea Philopator (; The name Cleopatra is pronounced , or sometimes in both British and American English, see and respectively. Her name was pronounced in the Greek dialect of Egypt (see Koine Greek phonology). She was ...
was married to two of her younger brothers,
Ptolemy XIII Ptolemy XIII Theos Philopator (, ''Ptolemaĩos''; c. 62 BC – 13 January 47 BC) was Pharaoh of Egypt from 51 to 47 BC, and one of the last members of the Ptolemaic dynasty (305–30 BC). He was the son of Ptolemy XII and the brother of and co ...
and
Ptolemy XIV Ptolemy XIV Philopator (, ; c. 59 – 44 BC) was a Pharaoh of the Ptolemaic Kingdom of Egypt, who reigned from 47 until his death in 44 BC. Biography Following the death of his older brother Ptolemy XIII of Egypt on January 13, 47 BC, and accor ...
, whilst her mother and father, Cleopatra V and Ptolemy XII, were also brother and sister.
Arsinoe II Arsinoë II (, 316 BC – between 270 and 268 BC) was Queen consort of Thrace, Anatolia, and Macedonia by her first and second marriage, to king Lysimachus and king Ptolemy Keraunos respectively, and then Queen of the Ptolemaic Kingdom of Egy ...
and her younger brother
Ptolemy II Philadelphus Ptolemy II Philadelphus (, ''Ptolemaîos Philádelphos'', "Ptolemy, sibling-lover"; 309 – 28 January 246 BC) was the pharaoh of Ptolemaic Egypt from 284 to 246 BC. He was the son of Ptolemy I, the Macedonian Greek general of Alexander the G ...
were the first in the family to participate in a full-sibling marriage, a departure from custom. A union between full siblings was counternormative in Greek and Macedonian tradition, and prohibited by the laws of at least some cities. The fable of ''
Oedipus Oedipus (, ; "swollen foot") was a mythical Greek king of Thebes. A tragic hero in Greek mythology, Oedipus fulfilled a prophecy that he would end up killing his father and marrying his mother, thereby bringing disaster to his city and family. ...
'', with a theme of inadvertent incest between a mother and son, ends in disaster and shows ancient taboos against incest, since Oedipus blinds himself in disgust and shame after his incestuous actions. In the 'sequel' to ''Oedipus'', ''
Antigone ANTIGONE (Algorithms for coNTinuous / Integer Global Optimization of Nonlinear Equations), is a deterministic global optimization solver for general Mixed-Integer Nonlinear Programs (MINLP). History ANTIGONE is an evolution of GloMIQO, a global ...
'', his four children are also punished for their parents' incestuousness. Incest appears in the commonly accepted version of the birth of
Adonis In Greek mythology, Adonis (; ) was the mortal lover of the goddesses Aphrodite and Persephone. He was considered to be the ideal of male beauty in classical antiquity. The myth goes that Adonis was gored by a wild boar during a hunting trip ...
, when his mother,
Myrrha Myrrha (; ), also known as Smyrna (), is the mother of Adonis in Greek mythology. She was transformed into a myrrh tree after having intercourse with her father, and gave birth to Adonis in tree form. Although the tale of Adonis has Semitic r ...
, has sex with her father,
Cinyras In Greek mythology, Cinyras (; – ''Kinyras'') was a famous hero and king of Cyprus. Accounts vary significantly as to his genealogy and provide a variety of stories concerning him; in many sources he is associated with the cult of Aphrodit ...
, during a festival, disguised as a
prostitute Prostitution is a type of sex work that involves engaging in sexual activity in exchange for payment. The definition of "sexual activity" varies, and is often defined as an activity requiring physical contact (e.g., sexual intercourse, non-pe ...
. In
ancient Greece Ancient Greece () was a northeastern Mediterranean civilization, existing from the Greek Dark Ages of the 12th–9th centuries BC to the end of classical antiquity (), that comprised a loose collection of culturally and linguistically r ...
, Spartan King
Leonidas I Leonidas I (; , ''Leōnídas''; born ; died 11 August 480 BC) was king of the Ancient Greek city-state of Sparta. He was the son of king Anaxandridas II and the 17th king of the Agiad dynasty, a Spartan royal house which claimed descent fro ...
, hero of the legendary
Battle of Thermopylae The Battle of Thermopylae ( ) was fought in 480 BC between the Achaemenid Empire, Achaemenid Persian Empire under Xerxes I and an alliance of Polis, Greek city-states led by Sparta under Leonidas I. Lasting over the course of three days, it wa ...
, was married to his
niece In the lineal kinship system used in the English-speaking world, a niece or nephew is a child of an individual's sibling or sibling-in-law. A niece is female and a nephew is male, and they would call their parents' siblings aunt or uncle ...
Gorgo, daughter of his half-brother
Cleomenes I Cleomenes I (; Greek Κλεομένης; died c. 490 BC) was Agiad King of Sparta from c. 524 to c. 490 BC. One of the most important Spartan kings, Cleomenes was instrumental in organising the Greek resistance against the Persian Empire of Da ...
. Greek law allowed marriage between a brother and sister if they had different mothers: for example, some accounts say that Elpinice was for a time married to her half-brother
Cimon Cimon or Kimon (; – 450BC) was an Athenian '' strategos'' (general and admiral) and politician. He was the son of Miltiades, also an Athenian ''strategos''. Cimon rose to prominence for his bravery fighting in the naval Battle of Salamis ...
. Incest is mentioned and condemned in
Virgil Publius Vergilius Maro (; 15 October 70 BC21 September 19 BC), usually called Virgil or Vergil ( ) in English, was an ancient Rome, ancient Roman poet of the Augustan literature (ancient Rome), Augustan period. He composed three of the most fa ...
's ''
Aeneid The ''Aeneid'' ( ; or ) is a Latin Epic poetry, epic poem that tells the legendary story of Aeneas, a Troy, Trojan who fled the Trojan War#Sack of Troy, fall of Troy and travelled to Italy, where he became the ancestor of the Ancient Rome ...
'' Book VI: ''hic thalamum invasit natae vetitosque hymenaeos'' "This one invaded a daughter's room and a forbidden sex act". Roman civil law prohibited marriages within four degrees of consanguinityPatrick Colquhoun, ''A Summary of the Roman Civil Law, Illustrated by Commentaries on and Parallels from the Mosaic, Canon, Mohammedan, English, and Foreign Law'' (London: Wm. Benning & Co., 1849), p. 513-4 but had no degrees of affinity with regard to marriage. Roman civil laws prohibited any marriage between parents and children, either in the ascending or descending line
ad infinitum ''Ad infinitum'' is a Latin phrase meaning "to infinity" or "forevermore". Description In context, it usually means "continue forever, without limit" and this can be used to describe a non-terminating process, a non-terminating ''repeating'' pro ...
. Adoption was considered the same as affinity in that an adoptive father could not marry an unemancipated daughter or granddaughter even if the adoption had been dissolved. Incestuous unions were discouraged and considered '' nefas'' (against the laws of gods and man) in
ancient Rome In modern historiography, ancient Rome is the Roman people, Roman civilisation from the founding of Rome, founding of the Italian city of Rome in the 8th century BC to the Fall of the Western Roman Empire, collapse of the Western Roman Em ...
. In AD 295, incest was explicitly forbidden by an imperial edict, which divided the concept of ''incestus'' into two categories of unequal gravity: the ''incestus iuris gentium'', which was applied to both Romans and non-Romans in the Empire, and the ''incestus iuris civilis'', which concerned only Roman citizens. Therefore, for example, an Egyptian could marry an aunt, but a Roman could not. Despite the act of incest being unacceptable within the Roman Empire, Roman Emperor
Caligula Gaius Caesar Augustus Germanicus (31 August 12 – 24 January 41), also called Gaius and Caligula (), was Roman emperor from AD 37 until his assassination in 41. He was the son of the Roman general Germanicus and Augustus' granddaughter Ag ...
is rumored to have had sexual relationships with all three of his sisters (
Julia Livilla Julia Livilla ( – ) was the youngest child of Germanicus and Agrippina the Elder and the youngest sister of the Emperor Caligula. Life Julia Livilla was the youngest great-granddaughter of Emperor Augustus, great-niece and adoptive grandda ...
, Drusilla, and
Agrippina the Younger Julia Agrippina (6 November AD 15 – 23 March AD 59), also referred to as Agrippina the Younger, was Roman empress from AD 49 to 54, the fourth wife and niece of emperor Claudius, and the mother of Nero. Agrippina was one of the most prominent ...
). Emperor
Claudius Tiberius Claudius Caesar Augustus Germanicus ( ; ; 1 August 10 BC – 13 October AD 54), or Claudius, was a Roman emperor, ruling from AD 41 to 54. A member of the Julio-Claudian dynasty, Claudius was born to Nero Claudius Drusus, Drusus and Ant ...
, after executing his previous wife, married his brother's daughter, Agrippina the Younger, and changed the law to allow an otherwise illegal union. The law prohibiting marrying a sister's daughter remained. The taboo against incest in ancient Rome is demonstrated by the fact that politicians would use charges of incest (often false charges) as insults and means of political disenfranchisement. In
Norse mythology Norse, Nordic, or Scandinavian mythology, is the body of myths belonging to the North Germanic peoples, stemming from Old Norse religion and continuing after the Christianization of Scandinavia as the Nordic folklore of the modern period. The ...
, there are themes of brothersister marriage, a prominent example being between
Njörðr In Norse mythology, Njörðr (Old Norse: ) is a god among the Vanir. Njörðr, father of the deities Freyr and Freyja by Sister-wife of Njörðr, his unnamed sister, was in an ill-fated marriage with the goddess Skaði, lives in Nóatún (myth ...
and his unnamed sister (perhaps
Nerthus In Germanic paganism, Nerthus is a goddess associated with a ceremonial wagon procession. Nerthus is attested by first century A.D. Roman historian Tacitus in his ethnographic work ''Germania''. In ''Germania'', Tacitus records that a group of G ...
), parents of
Freyja In Norse mythology, Freyja (Old Norse "(the) Lady") is a goddess associated with love, beauty, fertility, sex, war, gold, and seiðr (magic for seeing and influencing the future). Freyja is the owner of the necklace Brísingamen, rides a char ...
and
Freyr Freyr (Old Norse: 'Lord'), sometimes anglicized as Frey, is a widely attested Æsir, god in Norse mythology, associated with kingship, fertility, peace, prosperity, fair weather, and good harvest. Freyr, sometimes referred to as Yngvi-Freyr, was ...
.
Loki Loki is a Æsir, god in Norse mythology. He is the son of Fárbauti (a jötunn) and Laufey (mythology), Laufey (a goddess), and the brother of Helblindi and Býleistr. Loki is married to the goddess Sigyn and they have two sons, Narfi (son of Lo ...
in turn also accuses Freyja and Freyr of having a sexual relationship.


Biblical references

The earliest Biblical reference to possible incest involves Cain. It was cited that he knew his wife and she conceived and bore Enoch. A literalist reading of this passage indicates that, during this period, there was no other woman except Eve, or there was an unnamed sister, in which case Cain had an incestuous relationship with his mother or his sister. According to the
Book of Jubilees The Book of Jubilees is an ancient Jewish apocryphal text of 50 chapters (1,341 verses), considered canonical by the Ethiopian Orthodox Tewahedo Church, as well as by Haymanot Judaism, a denomination observed by members of Ethiopian Jewish ...
,
Cain Cain is a biblical figure in the Book of Genesis within Abrahamic religions. He is the elder brother of Abel, and the firstborn son of Adam and Eve, the first couple within the Bible. He was a farmer who gave an offering of his crops to God. How ...
married his sister Awan. Later, in Genesis 20 of the
Hebrew Bible The Hebrew Bible or Tanakh (;"Tanach"
. '' Patriarch The highest-ranking bishops in Eastern Orthodoxy, Oriental Orthodoxy, the Roman Catholic Church (above major archbishop and primate), the Hussite Church, Church of the East, and some Independent Catholic Churches are termed patriarchs (and ...
Abraham Abraham (originally Abram) is the common Hebrews, Hebrew Patriarchs (Bible), patriarch of the Abrahamic religions, including Judaism, Christianity, and Islam. In Judaism, he is the founding father who began the Covenant (biblical), covenanta ...
married his half-sister
Sarah Sarah (born Sarai) is a biblical matriarch, prophet, and major figure in Abrahamic religions. While different Abrahamic faiths portray her differently, Judaism, Christianity, and Islam all depict her character similarly, as that of a pious woma ...
. Other references include the passage in 2 Samuel 13 where
Amnon Amnon ( ''’Amnōn'', "faithful") was, in the Hebrew Bible, the oldest son of King David and his second wife, Ahinoam of Jezreel. He was born in Hebron during his father's reign in Judah. He was the heir apparent to the throne of Israel until ...
, King
David David (; , "beloved one") was a king of ancient Israel and Judah and the third king of the United Monarchy, according to the Hebrew Bible and Old Testament. The Tel Dan stele, an Aramaic-inscribed stone erected by a king of Aram-Dam ...
's son, rapes his half-sister Tamar. According to Michael D. Coogan, it would have been perfectly all right for Amnon to have married her, the Bible being inconsistent about prohibiting incest. In Genesis 19:3038, while living in an isolated area after the destruction of
Sodom and Gomorrah In the Abrahamic religions, Sodom and Gomorrah () were two cities destroyed by God for their wickedness. Sodom and Gomorrah are repeatedly invoked throughout the Hebrew Bible, Deuterocanonical texts, and the New Testament as symbols of sin, di ...
, Lot's two daughters conspire to inebriate and rape their father due to the lack of available partners to continue his line of descent. Because of intoxication, Lot "perceived not" when his firstborn, and the following night his younger, daughter lay with him. Moses was also born of an incestuous marriage. Exodus 6 details how his father,
Amram In the Book of Exodus, Amram (; ) is the husband of Jochebed and father of Aaron, Moses and Miriam. In the Holy Scriptures In addition to being married to Jochebed, Amram is also described in the Bible as having been related to Jochebed ...
, was the nephew of his mother,
Jochebed According to the Bible, Jochebed (; , lit. ' YHWH is glory') was a daughter of Levi and the mother of Miriam, Aaron, and Moses. She was the wife of Amram, as well as his aunt. No details are given concerning her life. According to Jewish legend ...
. An account noted that the incestuous relations did not suffer the fate of childlessness, which was the punishment for such couples in Levitical law. It stated, however, that the incest exposed Moses "to the peril of wild beasts, of the weather, of the water, and more."


From the Middle Ages onward

Many European monarchs were related due to political marriages, such that many such marriages were between cousins of some degree, uncles and nieces, and so forth, and sometimes first cousins. This was especially true in the
Habsburg The House of Habsburg (; ), also known as the House of Austria, was one of the most powerful dynasties in the history of Europe and Western civilization. They were best known for their inbreeding and for ruling vast realms throughout Europe d ...
,
Hohenzollern The House of Hohenzollern (, ; , ; ) is a formerly royal (and from 1871 to 1918, imperial) German dynasty whose members were variously princes, electors, kings and emperors of Hohenzollern, Brandenburg, Prussia, the German Empire, and Romania. ...
,
Savoy Savoy (; )  is a cultural-historical region in the Western Alps. Situated on the cultural boundary between Occitania and Piedmont, the area extends from Lake Geneva in the north to the Dauphiné in the south and west and to the Aosta Vall ...
, and Bourbon royal houses. However, relations between siblings, which may have been tolerated in other cultures, were considered abhorrent. For example, the false accusation that
Anne Boleyn Anne Boleyn (; 1501 or 1507 – 19 May 1536) was List of English royal consorts, Queen of England from 1533 to 1536, as the Wives of Henry VIII, second wife of King Henry VIII. The circumstances of her marriage and execution, by beheading ...
and her brother, George Boleyn, had committed incest was one of the reasons given for both being executed in May 1536. Historians agree that the false accusation against Anne Boleyn and George Boleyn was trumped up in order to ensure the king could go on to marry
Jane Seymour Jane Seymour (; 24 October 1537) was Queen of England as the third wife of King Henry VIII from their marriage on 30 May 1536 until her death the next year. She became queen following the execution of Henry's second wife, Anne Boleyn, who was ...
. Sects deemed heretical, such as the
Waldensians The Waldensians, also known as Waldenses (), Vallenses, Valdesi, or Vaudois, are adherents of a church tradition that began as an ascetic movement within Western Christianity before the Reformation. Originally known as the Poor of Lyon in the l ...
, were accused of incest. Incestuous marriages were also seen in the royal houses of ancient
Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...
and Korea, Inca
Peru Peru, officially the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Brazil, in the southeast by Bolivia, in the south by Chile, and in the south and west by the Pac ...
,
Ancient Hawaii Ancient Hawaii is the period of Hawaiian history preceding the establishment in 1795 of the Kingdom of Hawaii by Kamehameha the Great. Traditionally, researchers estimated the first settlement of the Hawaiian islands as having occurred sporad ...
, and, at times, Central Africa,
Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...
, and
Thailand Thailand, officially the Kingdom of Thailand and historically known as Siam (the official name until 1939), is a country in Southeast Asia on the Mainland Southeast Asia, Indochinese Peninsula. With a population of almost 66 million, it spa ...
. Like the kings of ancient Egypt, the
Inca The Inca Empire, officially known as the Realm of the Four Parts (, ), was the largest empire in pre-Columbian America. The administrative, political, and military center of the empire was in the city of Cusco. The History of the Incas, Inca ...
rulers married their sisters.
Huayna Capac Huayna Capac (; Cuzco Quechua: ''Wayna Qhapaq'' ) (before 14931527) was the third Sapa Inca of Tawantinsuyu, the Inca Empire. He was the son of and successor to Túpac Inca Yupanqui,Sarmiento de Gamboa, Pedro; 2015, originally published in Sp ...
, for instance, was the son of
Topa Inca Yupanqui Topa Inca Yupanqui or Túpac Inca Yupanqui (), also Topa Inga Yupangui, erroneously translated as "noble Inca accountant" (before 14711493) was the tenth Sapa Inca (1471–1493) of the Inca Empire, fifth of the Hanan dynasty. His father was Pac ...
and the Inca's sister and wife. Half-sibling marriages were found in ancient Japan, such as the marriage of Emperor Bidatsu and his half-sister
Empress Suiko (554 – 15 April 628) was the 33rd monarch of Japan,Imperial Household Agency (''Kunaichō''): She introduced Buddhism in Japan and built many Buddhist temples, but she held the balance between Buddhism and Shintoism. Under her rule, Japan ...
. Japanese Prince Kinashi no Karu had sexual relations with his full sister Princess Karu no Ōiratsume, although the action was regarded as foolish. In order to prevent the influence of the other families, Korean
Goryeo Goryeo (; ) was a Korean state founded in 918, during a time of national division called the Later Three Kingdoms period, that unified and ruled the Korea, Korean Peninsula until the establishment of Joseon in 1392. Goryeo achieved what has b ...
dynasty monarch Gwangjong married his half-sister Daemok in the 10th century. Marriage with a family member not related by blood was also regarded as contravening morality and was therefore incest. One example of this is the 14th century Chunghye of Goryeo, who raped one of his deceased father's concubines, who was thus regarded to be his mother. In a few parts of India, cousin marriage and uncle-niece marriage was common, though it has reduced a lot in the 21st century.


Others

In some Southeast Asian cultures, stories of incest being common among certain ethnicities are sometimes told as expressions of contempt for those ethnicities. Marriages between younger brothers and their older sisters were common among the early
Udege people The Udege (; or , or Udihe, Udekhe, and Udeghe correspondingly) are a native people of the Primorsky Krai and Khabarovsk Krai regions in Russia. They live along the tributaries of the Ussuri, Amur, Khungari, and Anyuy Rivers. The Udege spea ...
.


Prevalence and statistics

Incest between an adult and a person under the
age of consent The age of consent is the age at which a person is considered to be legally competent to consent to Human sexual activity, sexual acts. Consequently, an adult who engages in sexual activity with a person younger than the age of consent is un ...
is considered a form of
child sexual abuse Child sexual abuse (CSA), also called child molestation, is a form of child abuse in which an adult or older adolescent uses a child for sexual stimulation. Forms of child sexual abuse include engaging in Human sexual activity, sexual activit ...
that has been shown to be one of the most extreme forms of childhood abuse; it often results in serious and long-term
psychological trauma Psychological trauma (also known as mental trauma, psychiatric trauma, emotional damage, or psychotrauma) is an emotional response caused by severe distressing events, such as Major trauma, bodily injury, Sexual assault, sexual violence, or ot ...
, especially in the case of parental incest. Its prevalence is difficult to generalize, but research has estimated 10–15% of the general population as having had at least one such sexual contact, with less than 2% involving intercourse or attempted intercourse. Among women, research has yielded estimates as high as 20%.
Father A father is the male parent of a child. Besides the paternal bonds of a father to his children, the father may have a parental, legal, and social relationship with the child that carries with it certain rights and obligations. A biological fat ...
daughter A daughter is a female offspring; a girl or a woman in relation to her parents. Daughterhood is the state, condition or quality of being someone's daughter. The male counterpart is a son. Analogously the name is used in several areas to show r ...
incest was for many years the most commonly reported and studied form of incest.
Mother A mother is the female parent of a child. A woman may be considered a mother by virtue of having given birth, by raising a child who may or may not be her biological offspring, or by supplying her ovum for fertilisation in the case of ges ...
son incest is rarely reported. According to Catanzarite (1980), between 1965 and 1980 only a handful such cases were documented. Catanzarite attributes this to selection bias and the lack of physical evidence in such cases. According to Etherington (1997), one of the reasons of the under-reporting of such cases is that men often found difficulty in defining their mother's behavior as abuse. In a clinical study by Olson (1990), 30 men had been victims of incest; the mother was a perpetrator in 61.5 % of cases. In a clinical study by Kelly et al. (2002), among the 67 sexually abused men, in 17 cases the perpetrators were their mothers. More recently, studies have suggested that sibling incest, particularly older brothers having sexual relations with younger siblings, is the most common form of incest, with some studies finding sibling incest occurring more frequently than other forms of incest. Some studies suggest that adolescent perpetrators of sibling abuse choose younger victims, abuse victims over a lengthier period, use violence more frequently and severely than adult perpetrators, and that sibling abuse has a higher rate of penetrative acts than father or stepfather incest, with father and older brother incest resulting in greater reported distress than stepfather incest. South Africa, Saudi Arabia, Sudan, Pakistan, and Nigeria are some of the countries with the most incest through consanguineous marriage.


Types


Between adults and children

Sex between an adult family member and a child is usually considered a form of child sexual abuse, also known as child incestuous abuse, and for many years has been the most reported form of incest. Father–daughter and stepfather–stepdaughter sex are the most commonly reported forms of adult–child incest, with most of the remaining involving a mother or stepmother. Many studies found that stepfathers tend to be far more likely than biological fathers to engage in this form of incest. One study of adult women in San Francisco estimated that 17% of women were abused by stepfathers and 2% were abused by biological fathers. Father–son incest is reported less often, but it is not known how close the frequency is to heterosexual incest because it is probably more under-reported. The prevalence of incest between parents and their children is difficult to estimate due to secrecy and privacy. In a 1999 news story, the
BBC The British Broadcasting Corporation (BBC) is a British public service broadcaster headquartered at Broadcasting House in London, England. Originally established in 1922 as the British Broadcasting Company, it evolved into its current sta ...
reported: "Close-knit family life in India masks an alarming amount of sexual abuse of children and teenage girls by family members, a new report suggests. Delhi organisation RAHI said 76% of respondents to its survey had been abused when they were children 40% of those by a family member." According to the National Center for Victims of Crime a large proportion of
rape Rape is a type of sexual assault involving sexual intercourse, or other forms of sexual penetration, carried out against a person without consent. The act may be carried out by physical force, coercion, abuse of authority, or against a person ...
committed in the United States is perpetrated by a family member: Adults who as children were incestuously victimized by adults often suffer from low
self-esteem Self-esteem is confidence in one's own worth, abilities, or morals. Self-esteem encompasses beliefs about oneself (for example, "I am loved", "I am worthy") as well as emotional states, such as triumph, despair, pride, and shame. Smith and Macki ...
, difficulties in interpersonal relationships, and
sexual dysfunction Sexual dysfunction is difficulty experienced by an individual or partners during any stage of normal sexual activity, including physical pleasure, desire, preference, arousal, or orgasm. The World Health Organization defines sexual dysfunction ...
, and are at an extremely high risk of many mental disorders, including depression,
anxiety disorder Anxiety disorders are a group of mental disorders characterized by significant and uncontrollable feelings of anxiety and fear such that a person's social, occupational, and personal functions are significantly impaired. Anxiety may cause phys ...
s, phobic avoidance reactions, somatoform disorder,
substance abuse Substance misuse, also known as drug misuse or, in older vernacular, substance abuse, is the use of a drug in amounts or by methods that are harmful to the individual or others. It is a form of substance-related disorder, differing definition ...
,
borderline personality disorder Borderline personality disorder (BPD) is a personality disorder characterized by a pervasive, long-term pattern of significant interpersonal relationship instability, an acute fear of Abandonment (emotional), abandonment, and intense emotiona ...
, and
complex post-traumatic stress disorder Complex post-traumatic stress disorder (CPTSD, cPTSD, or hyphenated C-PTSD) is a stress-related mental disorder generally occurring in response to complex traumas (i.e., commonly prolonged (or repetitive) exposure to a traumatic event (or trau ...
. The Goler clan in
Nova Scotia Nova Scotia is a Provinces and territories of Canada, province of Canada, located on its east coast. It is one of the three Maritime Canada, Maritime provinces and Population of Canada by province and territory, most populous province in Atlan ...
is a specific instance in which child sexual abuse in the form of forced adultchild and siblingsibling incest took place over at least three generations. A number of Goler children were victims of sexual abuse at the hands of fathers, mothers, uncles, aunts, sisters, brothers, cousins, and each other. During interrogation by police, several of the adults openly admitted to engaging in many forms of sexual activity, up to and including full intercourse, multiple times with the children. Sixteen adults (both men and women) were charged with hundreds of allegations of incest and sexual abuse of children as young as five. In July 2012, twelve children were removed from the 'Colt' family (a pseudonym) in
New South Wales New South Wales (commonly abbreviated as NSW) is a States and territories of Australia, state on the Eastern states of Australia, east coast of :Australia. It borders Queensland to the north, Victoria (state), Victoria to the south, and South ...
, Australia, after the discovery of four generations of incest. Child protection workers and psychologists said interviews with the children indicated "a virtual sexual free-for-all". While incest between adults and children generally involves the adult as the perpetrator of abuse, there are rare instances of sons sexually assaulting their mothers. These sons are typically mid-adolescent to young adult, and, unlike parent-initiated incest, the incidents involve some kind of physical force. Although the mothers may be accused of being seductive with their sons and inviting the sexual contact, this is contrary to evidence. Such accusations can parallel other forms of rape, where, due to
victim blaming Victim blaming occurs when the victim of a crime or any wrongful act is held entirely or partially at fault for the harm that befell them. There is historical and current prejudice against the victims of domestic violence and sex crimes, such as ...
, a woman is accused of being at fault for the rape. In some cases, mother–son incest is best classified as acquaintance rape of the mother by the adolescent son.


Between children

Childhood sibling–sibling incest is considered to be widespread but rarely reported. Sibling–sibling incest becomes child-on-child sexual abuse when it occurs without consent, without equality, or as a result of
coercion Coercion involves compelling a party to act in an involuntary manner through the use of threats, including threats to use force against that party. It involves a set of forceful actions which violate the free will of an individual in order to i ...
. In this form, it is believed to be the most common form of intrafamilial abuse. The most commonly reported form of abusive sibling incest is abuse of a younger sibling by an older sibling. Sibling abusive incest is most prevalent in families where one or both parents are often absent or emotionally unavailable, with the abusive siblings using incest as a way to assert their power over a weaker sibling. Absence of the father in particular has been found to be a significant element of most cases of sexual abuse of female children by a brother.


Between adults

Proponents of incest between consenting adults draw clear boundaries between the behavior of consenting adults on one hand and rape, child molestation, and abusive incest on the other. However, even consensual relationships such as these are still legally classified as incest and criminalized in many jurisdictions (although there are certain exceptions). James Roffee, a senior lecturer in criminology at
Monash University Monash University () is a public university, public research university based in Melbourne, Victoria (state), Victoria, Australia. Named after World War I general Sir John Monash, it was founded in 1958 and is the second oldest university in the ...
and former worker on legal responses to familial sexual activity in England and Wales, and Scotland discussed how the
European Convention on Human Rights The European Convention on Human Rights (ECHR; formally the Convention for the Protection of Human Rights and Fundamental Freedoms) is a Supranational law, supranational convention to protect human rights and political freedoms in Europe. Draf ...
deems all familial sexual acts to be criminal, even if all parties give their full consent and are knowledgeable to all possible consequences. He also argues that the use of particular language tools in the legislation manipulates the reader to deem all familial sexual activities as immoral and criminal, even if all parties are consenting adults.


Aunts, uncles, moms, dads, nieces or nephews

In the
Netherlands , Terminology of the Low Countries, informally Holland, is a country in Northwestern Europe, with Caribbean Netherlands, overseas territories in the Caribbean. It is the largest of the four constituent countries of the Kingdom of the Nether ...
, marrying one's nephew or niece is legal, but only with the explicit permission of the Dutch government, due to the possible risk of genetic defects among the offspring. Nephew-niece marriages predominantly occur among foreign immigrants. In November 2008, the Scientific Institute of the Christian Democratic Party (CDA) announced that it wanted a ban on marriages to nephews and nieces. Consensual sex between individuals aged 18 and older is always lawful in the Netherlands and Belgium, even among closely related family members. Sexual acts between an adult family member and a minor are illegal, though they are classified not as incest but as abuse of the authority such an adult has over a minor, comparable to that of a teacher, coach, or priest. In
Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...
, consensual adult sexual intercourse with someone known to be one's aunt, uncle, niece, or nephew constitutes a felony of the third degree. Other states also commonly prohibit marriages between such kin. The legality of sex with a half-aunt or half-uncle varies state by state. In the United Kingdom, incest includes only sexual intercourse with a parent, grandparent, child, or sibling, but the more recently introduced offense of "sex with an adult relative" extends as far as half-siblings, uncles, aunts, nephews, and nieces. However, the term 'incest' remains widely used in popular culture to describe any form of sexual activity with a relative. In Canada, marriage between uncles and nieces and between aunts and nephews is illegal.


Between adult siblings

One of the most public cases of adult sibling incest in the 2000s is the case of Patrick Stübing and Susan Karolewski, a brothersister couple from Germany. Because of violent behavior on the part of his father, Patrick was taken in at the age of 3 by foster parents, who adopted him later. At the age of 23 he learned about his biological parents, contacted his mother, and met her and his then 16-year-old sister Susan for the first time. The now-adult Patrick moved in with his birth family shortly thereafter. After their mother died suddenly six months later, the siblings became intimately close, and had their first child together in 2001. By 2004, they had had four children together: Eric, Sarah, Nancy, and Sofia. The public nature of their relationship, and the repeated
prosecution A prosecutor is a legal representative of the prosecution in states with either the adversarial system, which is adopted in common law, or inquisitorial system, which is adopted in Civil law (legal system), civil law. The prosecution is the ...
s and jail time they have served as a result, have caused some in Germany to question whether incest between consenting adults should be punished at all. An article about them in ''
Der Spiegel (, , stylized in all caps) is a German weekly news magazine published in Hamburg. With a weekly circulation of about 724,000 copies in 2022, it is one of the largest such publications in Europe. It was founded in 1947 by John Seymour Chaloner ...
'' states that the couple are happy together. According to court records, the first three children have mental and physical disabilities, and have been placed in foster care. In April 2012, at the
European Court of Human Rights The European Court of Human Rights (ECtHR), also known as the Strasbourg Court, is an international court of the Council of Europe which interprets the European Convention on Human Rights (ECHR). The court hears applications alleging that a co ...
, Patrick Stübing lost his case that the conviction violated his right to a private and family life.Judgment
on the ''Stübing vs. Germany'' case.
European Court of Human Rights The European Court of Human Rights (ECtHR), also known as the Strasbourg Court, is an international court of the Council of Europe which interprets the European Convention on Human Rights (ECHR). The court hears applications alleging that a co ...
.
On 24 September 2014, the German Ethics Council recommended that the government abolish laws criminalizing incest between siblings, arguing that such bans impinge upon citizens. Some societies differentiate between full-sibling and half-sibling relations.


Cousin relationships

Marriages and sexual relationships between first cousins are stigmatized as incest in some cultures, but tolerated in much of the world. Currently, 24
US states In the United States, a state is a constituent political entity, of which there are 50. Bound together in a political union, each state holds governmental jurisdiction over a separate and defined geographic territory where it shares its so ...
prohibit marriages between first cousins, and another seven permit them only under special circumstances. The United Kingdom permits both marriage and sexual relations between first cousins. In some non-Western societies, marriages between close biological relatives account for 2060% of all marriages. First- and second-cousin marriages are rare in Western Europe, North America, and Oceania, accounting for less than 1% of marriages, but reach 9% in South America, East Asia, and South Europe, and about 50% in regions of the Middle East, North Africa, and South Asia. Communities such as the Dhond and the Bhittani of Pakistan clearly prefer marriages between cousins due to the belief they ensure purity of the descent line, provide intimate knowledge of the spouses, and ensure that patrimony will not pass into the hands of "outsiders". Cross-cousin marriages are preferred among the
Yanomami The Yanomami, also spelled Yąnomamö or Yanomama, are a group of approximately 35,000 indigenous people of the Americas, indigenous people who live in some 200–250 villages in the Amazon rainforest on the border between Venezuela and Brazil. ...
of Brazilian Amazonia, among many other tribal societies identified by anthropologists. There are some cultures in Asia which stigmatize cousin marriage, in some instances even marriages between second cousins or more remotely related people. This is notably true in the culture of
Korea Korea is a peninsular region in East Asia consisting of the Korean Peninsula, Jeju Island, and smaller islands. Since the end of World War II in 1945, it has been politically Division of Korea, divided at or near the 38th parallel north, 3 ...
. In South Korea, before 1997, two people with the same last name and clan were prohibited from marrying. In light of this law being held unconstitutional, South Korea now only prohibits up to third cousins (see Article 809 of the Korean Civil Code).
Hmong Hmong may refer to: * Hmong people, an ethnic group living mainly in Southwest China, Vietnam, Laos, and Thailand * Hmong cuisine * Hmong customs and culture ** Hmong music ** Hmong textile art * Hmong language, a continuum of closely related ...
culture prohibits the marriage of anyone with the same last name to do so would result in being shunned by the entire community, and they are usually stripped of their last name. In a review of 48 studies of children parented by cousins, the rate of birth defects was twice that of non-related couples: 4% for cousin couples as opposed to 2% for the general population.


Defined through marriage

Some cultures include relatives by marriage in incest prohibitions; these relationships are called
affinity Affinity may refer to: Commerce, finance and law * Affinity (law), kinship by marriage * Affinity analysis, a market research and business management technique * Affinity Credit Union, a Saskatchewan-based credit union * Affinity Equity Pa ...
rather than
consanguinity Consanguinity (from Latin '':wikt: consanguinitas, consanguinitas'' 'blood relationship') is the characteristic of having a kinship with a relative who is descended from a common ancestor. Many jurisdictions have laws prohibiting people who are ...
. For example, the question of the legality and morality of a widower who wished to marry his deceased wife's sister was the subject of long and fierce debate in the
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...
in the 19th century, involving, among others,
Matthew Boulton Matthew Boulton ( ; 3 September 172817 August 1809) was an English businessman, inventor, mechanical engineer, and silversmith. He was a business partner of the Scottish engineer James Watt. In the final quarter of the 18th century, the par ...
and
Charles La Trobe Charles Joseph La Trobe (20 March 18014 December 1875), commonly Latrobe, was appointed in 1839 superintendent of the Port Phillip District of New South Wales and, after the establishment in 1851 of the colony of Victoria (now a state of Aust ...
. The marriages were entered into in Scotland and Switzerland respectively, where they were legal. In medieval Europe, Lateran IV ruled that standing as a
godparent Within Christianity, a godparent or sponsor is someone who bears witness to a child's baptism (christening) and later is willing to help in their catechesis, as well as their lifelong spiritual formation. In both religious and civil views, ...
to a child also created a bond of affinity; which precluded legal marriage. But in other societies, a deceased spouse's sibling was considered the ideal person to marry. The Hebrew Bible forbids a man from marrying his brother's widow with the exception that, if his brother dies childless, the man is required to marry his brother's widow so as to "raise up seed to him". Some societies have long practiced sororal polygyny, a form of
polygamy Polygamy (from Late Greek , "state of marriage to many spouses") is the practice of marriage, marrying multiple spouses. When a man is married to more than one wife at the same time, it is called polygyny. When a woman is married to more tha ...
in which a man marries multiple wives who are sisters to each other (though not closely related to him). In Islamic law, marriage among close blood relations like parents, stepparents, parents in-law, siblings, stepsiblings, the children of siblings, aunts, and uncles is forbidden, while first or second cousins may marry. Marrying the widow of a brother or the sister of a deceased or divorced wife is also allowed.


Inbreeding

Offspring of biologically related parents are subject to the possible impact of inbreeding. Such offspring have a higher possibility of congenital birth defects (see
Coefficient of relationship The coefficient of relationship is a measure of the degree of consanguinity (or biological relationship) between two individuals. The term coefficient of relationship was defined by Sewall Wright in 1922, and was derived from his definition of th ...
), because it increases the proportion of zygotes that are
homozygous Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism. Mos ...
for deleterious
recessive allele In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and ...
s that produce such disorders (see
Inbreeding depression Inbreeding depression is the reduced biological fitness caused by loss of genetic diversity as a consequence of inbreeding, the breeding of individuals closely related genetically. This loss of genetic diversity results from small population siz ...
). Because most such
allele An allele is a variant of the sequence of nucleotides at a particular location, or Locus (genetics), locus, on a DNA molecule. Alleles can differ at a single position through Single-nucleotide polymorphism, single nucleotide polymorphisms (SNP), ...
s are rare in populations, it is unlikely that two unrelated marriage partners will both be heterozygous carriers. However, because close relatives share a large fraction of their alleles, the probability that any such rare deleterious allele present in the common ancestor will be inherited from both related parents is increased dramatically with respect to non-inbred couples. Contrary to common belief, inbreeding does not in itself alter allele frequencies, but rather increases the relative proportion of homozygotes to heterozygotes. This has two contrary effects: * In the short term, because incestuous reproduction increases
zygosity Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism. Mos ...
, deleterious recessive alleles will express themselves more frequently, leading to increases in spontaneous abortions of zygotes, perinatal deaths, and postnatal offspring with birth defects. * In the long run, however, because of this increased exposure of deleterious recessive alleles to
natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the Heredity, heritable traits characteristic of a population over generation ...
, their frequency decreases more rapidly in inbred population, leading to a "healthier" population (with fewer deleterious recessive alleles). The closer the relationship between two persons, the higher the zygosity, and thus the more severe the biological costs of inbreeding. This fact probably explains why inbreeding between close relatives, such as siblings, is less common than inbreeding between cousins. There may also be other deleterious effects besides those caused by recessive diseases. Thus, similar
immune system The immune system is a network of biological systems that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to bacteria, as well as Tumor immunology, cancer cells, Parasitic worm, parasitic ...
s may be more vulnerable to infectious diseases (see
Major histocompatibility complex and sexual selection Major histocompatibility complex (MHC) genes code for cell surface proteins that facilitate an organism's immune response to pathogens as well as its ability to avoid attacking its own cells. These genes have maintained an unusually high level of ...
). A 1994 study found a mean excess mortality with inbreeding among first cousins of 4.4%. A 2008 study also found decreased lifespan among offspring of first cousins, but no difference between lifespans after the second cousin level. A 1990 study conducted in South India found that the incidence of malformations was slightly higher in uncle-niece progeny (9.34%) compared to the first cousin progeny (6.18%). Stillbirth rates were significantly higher among consanguineous couples irrespective of the mother's socioeconomic status, and were higher in uncle-niece mating's compared to first cousin and beyond first cousin unions in both the poor and middle/upper class. Children of parentchild or siblingsibling unions are at increased risk compared to cousincousin unions. Studies suggest that 20–36% of these children will die or have major disability due to the inbreeding. A study of 29 offspring resulting from brothersister or fatherdaughter incest found that 20 had congenital abnormalities, including four directly attributable to autosomal recessive alleles.


Laws

Laws regarding sexual activity between close relatives vary considerably between jurisdictions, and depend on the type of sexual activity and the nature of the family relationship of the parties involved, as well as the age and sex of the parties. Prohibition of incest laws may extend to restrictions on marriage rights, which also vary between jurisdictions. Most jurisdictions prohibit parentchild and sibling marriages, while others also prohibit first-cousin and uncleniece and auntnephew marriages. In most places, incest is illegal, regardless of the ages of the two partners. In other countries, incestuous relationships between consenting adults (with the age varying by location) are permitted, including in the
Netherlands , Terminology of the Low Countries, informally Holland, is a country in Northwestern Europe, with Caribbean Netherlands, overseas territories in the Caribbean. It is the largest of the four constituent countries of the Kingdom of the Nether ...
,
France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...
,
Slovenia Slovenia, officially the Republic of Slovenia, is a country in Central Europe. It borders Italy to the west, Austria to the north, Hungary to the northeast, Croatia to the south and southeast, and a short (46.6 km) coastline within the Adriati ...
, and
Spain Spain, or the Kingdom of Spain, is a country in Southern Europe, Southern and Western Europe with territories in North Africa. Featuring the Punta de Tarifa, southernmost point of continental Europe, it is the largest country in Southern Eur ...
.
Sweden Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic count ...
is the only country that allows marriage between half-siblings, and they must seek government counseling before marriage. While the legality of consensual incest varies by country, sexual assault committed against a relative is seen as a very serious crime. In some legal systems, the fact of a perpetrator being a close relative to the victim constitutes an aggravating circumstance in the case of sexual crimes such as
rape Rape is a type of sexual assault involving sexual intercourse, or other forms of sexual penetration, carried out against a person without consent. The act may be carried out by physical force, coercion, abuse of authority, or against a person ...
and sexual conduct with a minor– this is the case in
Romania Romania is a country located at the crossroads of Central Europe, Central, Eastern Europe, Eastern and Southeast Europe. It borders Ukraine to the north and east, Hungary to the west, Serbia to the southwest, Bulgaria to the south, Moldova to ...
.


Religious and philosophical views


Judaism

The first religious resource found that prohibits incest, is the Torah, in book of Leviticus, chapter 18, "the children of Israel" Israelite men and women alike are forbidden from sexual relations between people who are "near of kin" (verse 6), who are defined as: * Children and their mothers (verse 7); * Siblings and half-siblings (verses 9 and 11). Relationships between these are particularly singled out for a curse i
Deuteronomy 27
and they are of the only two kinds of incestuous relationships that are among the particularly singled-out relationships with the other particularly singled-out relationships being ones of non-incestuous family betrayal (cf. verse 20) and bestiality (cf. verse 21); * Grandparents and grandchildren (verse 10); * Aunts and nephews, uncles and nieces, etc. (verses 12–14). Relationships between these are the second kind of relationships that are particularly singled out for a curse i

and the explicit examples of children-in-law and mothers-in-law (verse 23) serve to remind the Israelites that the parents-in-law are also (or at least should also be) the children-in-law's aunts and uncles:
And Moses commanded the children of Israel according to the word of the LORD, saying: 'The tribe of the sons of Joseph speaketh right. This is the thing which the LORD hath commanded concerning the daughters of Zelophehad, saying: Let them be married to whom they think best; only into the family of the tribe of their father shall they be married. So shall no inheritance of the children of Israel remove from tribe to tribe; for the children of Israel shall cleave every one to the inheritance of the tribe of his fathers. And every daughter, that possesseth an inheritance in any tribe of the children of Israel, shall be wife unto one of the family of the tribe of her father, that the children of Israel may possess every man the inheritance of his fathers. So shall no inheritance remove from one tribe to another tribe; for the tribes of the children of Israel shall cleave each one to its own inheritance.' Even as the LORD commanded Moses, so did the daughters of Zelophehad. For Mahlah, Tirzah, and Hoglah, and Milcah, and Noah, the daughters of Zelophehad, were married unto their father's brothers' sons.
Incestuous relationships, along with the other forbidden relationships that are mentioned in Leviticus 18, are considered so severe among ''chillulim HaShem'', acts which bring shame to the name of God, as to be punishable by death as specified i
Leviticus 20
In the 4th century BC, the Soferim (''scribes'') declared that there were relationships within which marriage constituted incest, in addition to those mentioned by the Torah. These additional relationships were termed ''seconds'' (Hebrew: ''sheniyyot'') and included the wives of a man's grandfather and grandson.Yebamot (
Tosefta The Tosefta ( "supplement, addition") is a compilation of Jewish Oral Law from the late second century, the period of the Mishnah and the Jewish sages known as the '' Tannaim''. Background Jewish teachings of the Tannaitic period were cha ...
) 2:3
The classical rabbis prohibited marriage between a man and any of these ''seconds'' of his, on the basis that doing so would act as a ''safeguard'' against infringing the biblical incest rules,Yebamot 21a although there was inconclusive debate about exactly what the limits should be for the definition of ''seconds''. Marriages that are forbidden in the Torah (with the exception of uncleniece marriages) were regarded by the rabbis of the Middle Ages as invalid– as if they had never occurred;'' Shulchan 'Aruk'', ''Eben ha-'Ezer'', 16, 1 any children born to such a couple were regarded as bastards under Jewish law, and the relatives of the spouse were not regarded as forbidden relations for further marriage. On the other hand, relationships that were prohibited due to qualifying as ''seconds'' and so forth were regarded as wicked but still valid; while such a couple may have been pressured to divorce, any children of the union were still seen as legitimate.


Christianity

The New Testament condemns relations between a man "and his father's wife" (1 Corinthians 5:15). It is inevitable for Bible literalists to accept that the first children of Adam and Eve would have been in incestuous relations as we regard it today. However, according to the Bible, God's law forbidding incest had not at that time been given to men and was delivered to Moses after Adam and Eve were created. Protestant Christians who adopt the Old Testament as part of their rule of faith and practice distinguish between the ceremonial law and the moral law given to Moses, with the demands of the ceremonial law being fulfilled by Christ's atoning death. Protestants view Leviticus 18:620 as part of the moral law and still applicable, thus condemning sexual/marriage relations between a man and his mother, sister, stepsister, or stepmother (if a man has more than one wife, it is forbidden for a son to have relations with or marry any of his father's wives), aunt, granddaughter, or his brother's wife. Leviticus 18 goes on to condemn relations between a man and the daughter of a woman he is having relations with and the sister of a woman he has had sexual relations with while the first sister is still alive. The
Book of Common Prayer The ''Book of Common Prayer'' (BCP) is the title given to a number of related prayer books used in the Anglican Communion and by other Christianity, Christian churches historically related to Anglicanism. The Book of Common Prayer (1549), fi ...
of the
Anglican Communion The Anglican Communion is a Christian Full communion, communion consisting of the Church of England and other autocephalous national and regional churches in full communion. The archbishop of Canterbury in England acts as a focus of unity, ...
allows marriages up to and including first cousins. The
Catholic Church The Catholic Church (), also known as the Roman Catholic Church, is the List of Christian denominations by number of members, largest Christian church, with 1.27 to 1.41 billion baptized Catholics Catholic Church by country, worldwid ...
regards incest as a sin against the Sacrament of Matrimony. For the Catholic Church, at the heart of the immorality of incest is the corruption and disordering of proper family relations. These disordered relationships take on a particularly grave and immoral character when it becomes
child sexual abuse Child sexual abuse (CSA), also called child molestation, is a form of child abuse in which an adult or older adolescent uses a child for sexual stimulation. Forms of child sexual abuse include engaging in Human sexual activity, sexual activit ...
. As the ''
Catechism of the Catholic Church The ''Catechism of the Catholic Church'' (; commonly called the ''Catechism'' or the ''CCC'') is a reference work that summarizes the Catholic Church's doctrine. It was Promulgation (Catholic canon law), promulgated by Pope John Paul II in 1992 ...
'' says:
2388 ''Incest'' designates intimate relations between relatives or in-laws within a degree that prohibits marriage between them. St. Paul stigmatizes this especially grave offense: 'It is actually reported that there is immorality among you...for a man is living with his father's wife...In the name of the Lord Jesus...you are to deliver this man to Satan for the destruction of the flesh....' Incest corrupts family relationships and marks a regression toward animality. 2389 Connected to incest is any sexual abuse perpetrated by adults on children or adolescents entrusted to their care. The offense is compounded by the scandalous harm done to the physical and moral integrity of the young, who will remain scarred by it all their lives; and the violation of responsibility for their upbringing.


Islam

The
Quran The Quran, also Romanization, romanized Qur'an or Koran, is the central religious text of Islam, believed by Muslims to be a Waḥy, revelation directly from God in Islam, God (''Allah, Allāh''). It is organized in 114 chapters (, ) which ...
gives specific rules regarding incest, which prohibit a man from marrying or having sexual relationships with: * his father's wife (his mother, or stepmother, his mother-in-law, a woman from whom he has nursed, even the children of this woman); * either parent's sister (aunt); * his sister, his half-sister, a woman who has nursed from the same woman as him, and his sister-in-law (wife's sister) while still married. Half relations are as sacred as full relations; * his niece (child of sibling); * his daughter, his stepdaughter (if the marriage to her mother was
consummated The consummation of a marriage, or simply consummation, is the first officially credited act of sexual intercourse following marriage. In many traditions and statutes of civil or religious law, the definition usually refers to penile–vaginal p ...
), his daughter-in-law. Cousin marriage finds support in Islamic scriptures and is widespread in the Middle East. Although Islam allows cousin marriage, there are
hadith Hadith is the Arabic word for a 'report' or an 'account f an event and refers to the Islamic oral tradition of anecdotes containing the purported words, actions, and the silent approvals of the Islamic prophet Muhammad or his immediate circle ...
s attributed to Muhammad calling for distance from the marriage of relatives. However, Muslim scholars generally consider these hadiths unreliable.


Zoroastrian

In
Ancient Persia The history of Iran (also known as Persia) is intertwined with Greater Iran, which is a socio-cultural region encompassing all of the areas that have witnessed significant settlement or influence exerted by the Iranian peoples and the Iranian ...
, incest between cousins is a blessed virtue, although, in some sources, incest is believed to be related to that of parentchild or brothersister. Under
Zoroastrianism Zoroastrianism ( ), also called Mazdayasnā () or Beh-dīn (), is an Iranian religions, Iranian religion centred on the Avesta and the teachings of Zoroaster, Zarathushtra Spitama, who is more commonly referred to by the Greek translation, ...
, royalty, clergy, and commoners practiced incest, though the extent in the lattermost class was unknown. This tradition was called
Xwedodah Xwedodah ( ; Avestan: ) is a type of consanguine marriage historically practiced in Zoroastrianism before the Muslim conquest of Persia. Such marriages are recorded as having been inspired by Zoroastrian cosmogony and considered pious. It was a ...
(). The tradition was considered so sacred that the bodily fluids produced by an incestuous couple were thought to have curative powers. For instance, the
Vendidad The Vendidad /ˈvendi'dæd/, also known as Videvdat, Videvdad or Juddēvdād, is a collection of texts within the greater compendium of the Avesta. However, unlike the other texts of the Avesta, the ''Vendidad'' is an ecclesiastical code, not a ...
advised corpse-bearers to purify themselves with a mixture of the urine of a married incestuous couple.
Friedrich Nietzsche Friedrich Wilhelm Nietzsche (15 October 1844 – 25 August 1900) was a German philosopher. He began his career as a classical philology, classical philologist, turning to philosophy early in his academic career. In 1869, aged 24, Nietzsche bec ...
, in his book '' The Birth of Tragedy'', cited that among Zoroastrians, a wise priest is born only by Xvaetvadatha. To what extent Xvaetvadatha was practiced in
Sasanian The Sasanian Empire (), officially Eranshahr ( , "Empire of the Iranians"), was an Iranian empire that was founded and ruled by the House of Sasan from 224 to 651. Enduring for over four centuries, the length of the Sasanian dynasty's reign ...
Iran and before especially outside the royal and noble families ("dynastic incest") and, perhaps, the clergy and whether practices ascribed to them can be assumed to be characteristic of the general population is not clear. There is a lack of genealogies and census material on the frequency of Xvaetvadatha.Fischer, Michael MJ. "Ptolemaic Jouissance and the Anthropology of Kinship: A Commentary on Ager" The Power of Excess: Royal Incest and the Ptolemaic Dynasty"." Anthropologica 49, no. 2 (2007): 295–299. Evidence from
Dura-Europos Dura-Europos was a Hellenistic, Parthian Empire, Parthian, and Ancient Rome, Roman border city built on an escarpment above the southwestern bank of the Euphrates river. It is located near the village of Al-Salihiyah, Deir ez-Zor Governorate, S ...
, however, combined with that of the Jewish and Christian sources citing actual cases under the Sasanians, strengthens the evidence of the Zoroastrian texts. In the post-Sasanian Zoroastrian literature, Xvaetvadatha is said to refer to marriages between cousins instead, which have always been relatively common. It has been observed that such incestuous acts received a great deal of glorification as a religious practice and, in addition to being condemned by foreigners (though the reliability of these accusations is questionable since accusations of incest were a common way of denigrating other groups), were considered a great challenge by their own proponents, with accounts suggesting that four copulations was deemed a rare achievement worthy of eternal salvation. It has been suggested that because taking up incestuous relations was a great personal challenge, seemingly repugnant even to Zoroastrians of the time, it served as an
honest signal Within evolutionary biology, signalling theory is a body of theoretical work examining communication between individuals, both within species and across species. The central question is how organisms with conflicting interests, such as in se ...
of commitment and devotion to religious ideals.


Hinduism

Rigveda The ''Rigveda'' or ''Rig Veda'' (, , from wikt:ऋच्, ऋच्, "praise" and wikt:वेद, वेद, "knowledge") is an ancient Indian Miscellany, collection of Vedic Sanskrit hymns (''sūktas''). It is one of the four sacred canoni ...
regards incest to be "evil".
Hinduism Hinduism () is an Hypernymy and hyponymy, umbrella term for a range of Indian religions, Indian List of religions and spiritual traditions#Indian religions, religious and spiritual traditions (Sampradaya, ''sampradaya''s) that are unified ...
speaks of incest in abhorrent terms. Hindus believe there are both karmic and practical bad effects of incest and thus practice strict rules of both
endogamy Endogamy is the cultural practice of marrying 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 relatio ...
and
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 tw ...
in relation to the family tree (''
gotra In Hindu culture, the term gotra (Sanskrit: गोत्र) is considered to be equivalent to lineage. It broadly refers to people who are descendants in an unbroken male line from a common male ancestor or patriline. Generally, the gotr ...
'') or bloodline ('' Pravara''). Marriage within the ''gotra'' (''swagotra'' marriage) is banned under the rule of exogamy in the traditional matrimonial system. People within the ''gotra'' are regarded as kin, and marrying such a person would be thought of as incest. Marriage with paternal cousins (a form of parallel-cousin relationship) is strictly prohibited. Traditional Hindu laws of marriage suggest that, between a man and a woman who are about to marry, there should be no common ancestor (gotra) between the groom and the bride for up to 6 generations on the father's side of the groom and bride and up to 4 generations on the mothers' side of the groom and bride. Some orthodox Hindus might extend this limit to up to 8 generations on the father's side and six generations on the mother's side (for both the bride and groom). Although marriages between persons having the same ''gotra'' are generally frowned upon, how this is defined may vary regionally. Depending on the culture and
caste A caste is a Essentialism, fixed social group into which an individual is born within a particular system of social stratification: a caste system. Within such a system, individuals are expected to marry exclusively within the same caste (en ...
of the population in the region, marriage may be restricted up to seven generations of ''gotra'' of father, mother, and grandmother. Marriage is banned within the same local community in a few rural areas.


Stoicism

The founder of
Stoicism Stoicism is a school of Hellenistic philosophy that flourished in ancient Greece and Rome. The Stoics believed that the universe operated according to reason, ''i.e.'' by a God which is immersed in nature itself. Of all the schools of ancient ...
,
Zeno of Citium Zeno of Citium (; , ; c. 334 – c. 262 BC) was a Hellenistic philosophy, Hellenistic philosopher from Kition, Citium (, ), Cyprus. He was the founder of the Stoicism, Stoic school of philosophy, which he taught in Athens from about 300 BC. B ...
, stated that incest was permissible in ''
Republic A republic, based on the Latin phrase ''res publica'' ('public affair' or 'people's affair'), is a State (polity), state in which Power (social and political), political power rests with the public (people), typically through their Representat ...
'', as did the later prominent Stoic philosopher
Chrysippus Chrysippus of Soli (; , ; ) was a Ancient Greece, Greek Stoicism, Stoic Philosophy, philosopher. He was a native of Soli, Cilicia, but moved to Athens as a young man, where he became a pupil of the Stoic philosopher Cleanthes. When Cleanthes ...
. However, Zeno only advocates for incest under unique circumstances, such as procreating with one's ailing mother to beget "glorious" children, thus comforting her. Otherwise, incest is condemned as being contrary to Nature. Zeno further condemns incest from a moral and psychological perspective, considering it to be a sign of
Plato Plato ( ; Greek language, Greek: , ; born  BC, died 348/347 BC) was an ancient Greek philosopher of the Classical Greece, Classical period who is considered a foundational thinker in Western philosophy and an innovator of the writte ...
's tyrannical soul, defined as a soul that is governed by illimitable desire. He uses
Oedipus Oedipus (, ; "swollen foot") was a mythical Greek king of Thebes. A tragic hero in Greek mythology, Oedipus fulfilled a prophecy that he would end up killing his father and marrying his mother, thereby bringing disaster to his city and family. ...
as a tragic example. Nonetheless, later Stoic disciples by the 1st century BC downplayed the pro-incest advocacy, accusing Zeno of being "young and thoughtless" when he wrote ''Republic''.


Animals

Inbreeding avoidance is rare in non-human animals.
North Carolina State University North Carolina State University (NC State, North Carolina State, NC State University, or NCSU) is a public university, public Land-grant university, land-grant research university in Raleigh, North Carolina, United States. Founded in 1887 and p ...
found that
bed bug Bed bugs are parasitic insects from the genus ''Cimex'', which are micropredators that haematophagy, feed on blood, usually at night. Their bites can result in a number of health impacts, including skin rashes, psychological effects, and aller ...
s, in contrast to most other insects, tolerate incest and are able to genetically withstand the effects of inbreeding quite well. Many species of
mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...
s, including humanity's closest
primate Primates is an order (biology), order of mammals, which is further divided into the Strepsirrhini, strepsirrhines, which include lemurs, galagos, and Lorisidae, lorisids; and the Haplorhini, haplorhines, which include Tarsiiformes, tarsiers a ...
relatives, tend to avoid mating with close relatives, especially if there are alternative partners available. However, some chimpanzees have been recorded attempting to mate with their mothers. Male rats have been recorded engaging in mating with their sisters, but they tend to prefer non-related females over their sisters.Sexual Behaviour In Animals
A. Sarkar; retrieved 29 January 2012
Livestock Livestock are the Domestication, domesticated animals that are raised in an Agriculture, agricultural setting to provide labour and produce diversified products for consumption such as meat, Egg as food, eggs, milk, fur, leather, and wool. The t ...
breeders often practice controlled breeding to eliminate undesirable characteristics within a population, which is also coupled with the
culling Culling is the process of segregating organisms from a group according to desired or undesired characteristics. In animal breeding, it is removing or segregating animals from a breeding stock based on a specific trait. This is done to exagge ...
of what is considered unfit offspring, especially when trying to establish a new and desirable trait in the stock.


See also

* Accidental incest * Adelphogamy *
Avunculate marriage An avunculate marriage (or uncle/aunt-niece/nephew marriage) is a marriage with a parent's sibling or with one's sibling's child—i.e., between an uncle or aunt and their niece or nephew. Such a marriage may occur between biological (consangu ...
*
Genetic distance Genetic distance is a measure of the genetics, genetic divergence between species or between population#Genetics, populations within a species, whether the distance measures time from common ancestor or degree of differentiation. Populations with ...
*
Genetic diversity Genetic diversity is the total number of genetic characteristics in the genetic makeup of a species. It ranges widely, from the number of species to differences within species, and can be correlated to the span of survival for a species. It is d ...
*
Genetic sexual attraction Genetic sexual attraction is a hypothesis that attraction may be a product of genetic similarities. While there is scientific evidence for the position, some commentators regard the hypothesis as pseudoscience. The term is also used for a phenome ...
* Incest between twins *
Incest taboo Incest ( ) is sex between close relatives, for example a brother, sister, or parent. This typically includes sexual activity between people in consanguinity (blood relations), and sometimes those related by lineage. It is condemned and con ...
* Incest in folklore and mythology * Incest in literature * Incest in media * List of coupled siblings *
Prohibited degree of kinship In law, a prohibited degree of kinship refers to a degree of consanguinity (blood relatedness), or sometimes affinity (relation by marriage or sexual relationship) between persons that makes sex or marriage between them illegal. An incest taboo ...
*
Proximity of blood Proximity of blood, or proximity by degree of kinship, is one of the ways to determine hereditary succession based on genealogy. In effect, the application of this rule is a refusal to recognize the right of representation, a component of primog ...
* *
Watta satta Watta satta or Shighar (, ) is an exchange marriage common in Pakistan and Afghanistan.Watta ...
*
Westermarck effect The Westermarck effect, also known as reverse sexual imprinting, is a psychological hypothesis that states that people tend not to be Sexual attraction, attracted to peers with whom they lived like siblings before the age of six. This hypothesi ...
which prevents most incest


References

;Citations ;Bibliography * * * Bixler, Ray H. (1982) "Comment on the Incidence and Purpose of Royal Sibling Incest," ''American Ethnologist'', ''9''(3), August, pp. 580–582. * Leavitt, G. C. (1990) "Sociobiological explanations of incest avoidance: A critical claim of evidential claims", ''American Anthropologist'', 92: 971–993. * * Sacco, Lynn (2009). ''Unspeakable: Father–Daughter Incest in American History''. Johns Hopkins University Press. 351 * Indrajit Bandyopadhyay (29 October 2008). "A Study In Folk "Mahabharata": How Balarama Became Abhimanyu's Father-in-law". ''Epic India: A New Arts & Culture Magazine'' * Đõ, Quý Toàn; Iyer, Sriya; Joshi, Shareen (2006). The Economics of Consanguineous Marriages. World Bank, Development Research Group, Poverty Team. *
link pp. 30–31
*


External links

* {{Authority control Family law Sex crimes