It is condemned and considered immoral in most societies, given that it can lead to an increased risk of genetic disorders in children in case of pregnancy from incestuous sex.
[20] Before the Latin term came in, incest was known in Old English 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.
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.
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.
[39] Incest is mentioned and condemned in Virgil's Aeneid Book VI:[40] hic thalamum invasit natae vetitosque hymenaeos – "This one invaded a daughter's room and a forbidden sex act".
[42] 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.
[51] In Genesis 19:30–38, 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.
[63] In India, the largest proportion of women aged 13 to 49 who marry their close relatives are in Tamil Nadu, then Andhra Pradesh, Karnataka, and Maharashtra.
It was also stated that the incest experience was psychologically harmful to the woman in later life, frequently leading to low self-esteem, very unhealthy sexual activity, contempt for other women, and other emotional problems.
[70][104][105] The Goler clan in Nova Scotia is a specific instance in which child sexual abuse in the form of forced adult–child and sibling–sibling incest took place over at least three generations.
[106] 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.
[122] 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.
[123] In the Netherlands, 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.
[128] In the United Kingdom, incest includes only sexual intercourse with a parent, grandparent, child, or sibling,[129] but the more recently introduced offense of "sex with an adult relative" extends as far as half-siblings, uncles, aunts, nephews, and nieces.
The public nature of their relationship, and the repeated prosecutions 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.
[131][132] 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.
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 in the 19th century, involving, among others, Matthew Boulton[146][147] and Charles La Trobe.
In medieval Europe, Lateran IV ruled that standing as a godparent to a child also created a bond of affinity; which precluded legal marriage.
[149] Some societies have long practiced sororal polygyny, a form of polygamy in which a man marries multiple wives who are sisters to each other (though not closely related to him).
Such offspring have a higher possibility of congenital birth defects (see Coefficient of relationship), because it increases the proportion of zygotes that are homozygous for deleterious recessive alleles that produce such disorders[150] (see Inbreeding depression).
In other countries, incestuous relationships between consenting adults (with the age varying by location) are permitted, including in the Netherlands, France, Slovenia, and Spain.
[168] On the other hand, relationships that were prohibited due to qualifying as seconds and so forth were regarded as wicked but still valid;[167] while such a couple may have been pressured to divorce, any children of the union were still seen as legitimate.
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.
[171]The Quran gives specific rules regarding incest, which prohibit a man from marrying or having sexual relationships with: Cousin marriage finds support in Islamic scriptures and is widespread in the Middle East.
[186] 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),[187] 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 of commitment and devotion to religious ideals.
[193] 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.
[196] North Carolina State University found that bed bugs, in contrast to most other insects, tolerate incest and are able to genetically withstand the effects of inbreeding quite well.
[200] Livestock breeders often practice controlled breeding to eliminate undesirable characteristics within a population, which is also coupled with the culling of what is considered unfit offspring, especially when trying to establish a new and desirable trait in the stock.