Incest
Incest is sex between close relatives, such as a brother, sister, or parent. This typically includes any kind of sexual activity between people in consanguinity, 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 in children in case of pregnancy from incestuous sex.
The incest taboo is one of the most widespread of all cultural taboos, both in present and in past societies. Most modern societies have laws regarding incest or social restrictions on closely consanguineous marriages. In societies where it is illegal, consensual adult incest is seen by some as a victimless crime. 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 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, 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, a collection of genetic disorders 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, a measure of how closely the parents are related genetically. However, cultural anthropologists have noted that inbreeding avoidance 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, brother-sister, father-daughter, mother-son, cousin-cousin, aunt-nephew, uncle-niece, and other combinations of relations within a royal family were married as a means of perpetuating the royal lineage, or echoing the practices in their creation myths, and were considered normal. Some societies have different views about what constitutes illegal or immoral incest. For example, in Samoa, a man was permitted to marry his older sister, but not his younger sister. However, sexual relations with a first-degree relative were almost universally forbidden in connection with multiple cases of disorders and organ failures.
Terminology
The English word incest is derived from the Latin incestus, which has a general meaning of "impure, unchaste". It was introduced into Middle English, both in the generic Latin sense 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 as sib-leger or mǣġhǣmed 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, first cousins with the same surnames were not permitted to marry, while those with different surnames could marry.In Achaemenid Persia, 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, Shah Cambyses II supposedly married two of his sisters, Atossa and Roxane. This would have been regarded as illegal. However, Herodotus also states that Cambyses married Otanes' daughter Phaidyme, whilst his contemporary Ctesias 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 kings married their sisters and had several children with them to continue the royal bloodline. For example, Tutankhamun married his half-sister Ankhesenamun, and was himself the child of an incestuous union between Akhenaten 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 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 was married to two of her younger brothers, Ptolemy XIII and Ptolemy XIV, whilst her mother and father, Cleopatra V and Ptolemy XII, were also brother and sister. Arsinoe II and her younger brother Ptolemy II Philadelphus 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.
File:Tutankhamun and his wife B. C. 1330.jpg|thumb|Egyptian king Tutankhamun married his half-sister Ankhesenamun.
The fable of Oedipus, 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, his four children are also punished for their parents' incestuousness. Incest appears in the commonly accepted version of the birth of Adonis, when his mother, Myrrha, has sex with her father, Cinyras, during a festival, disguised as a prostitute.
In ancient Greece, Spartan King Leonidas I, hero of the legendary Battle of Thermopylae, was married to his niece Gorgo, daughter of his half-brother Cleomenes I. 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.
Incest is mentioned and condemned in Virgil's Aeneid Book VI: hic thalamum invasit natae vetitosque hymenaeos "This one invaded a daughter's room and a forbidden sex act".
File:Yaxchilán lintel.jpg|thumb|Maya king Shield Jaguar II with his aunt-wife, Lady Xoc AD 709
Roman civil law prohibited marriages within four degrees of consanguinity 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. 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 in ancient Rome. 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 is rumored to have had sexual relationships with all three of his sisters. Emperor Claudius, 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 as insults and means of political disenfranchisement.
In Norse mythology, there are themes of brothersister marriage, a prominent example being between Njörðr and his unnamed sister, parents of Freyja and Freyr. Loki 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, Cain married his sister Awan. Later, in Genesis 20 of the Hebrew Bible, the Patriarch Abraham married his half-sister Sarah. Other references include the passage in 2 Samuel 13 where Amnon, King David'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, 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, was the nephew of his mother, Jochebed. 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."