Incest (/ˈɪnsɛst/ IN-sest) is sex between close relatives, for example
a brother or sister or cousins.[1][2] This typically includes sexual activity between people
in consanguinity (blood relations), and sometimes those related by lineage. 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.
The incest taboo is one of the most widespread of all cultural taboos, both in present
and in past societies.[3] Most modern societies have laws regarding incest or social
restrictions on closely consanguineous marriages.[3] In societies where it is illegal,
consensual adult incest is seen by some as a victimless crime.[4][5] Some cultures extend
the incest taboo to relatives with no consanguinity, such as milk-siblings, stepsiblings,
and adoptive siblings, albeit sometimes with less intensity.[6][7] 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.[8] Children of incestuous
relationships have been regarded as illegitimate,[where?] 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.
[9]
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.[9][10] 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.[9][11][12][13]
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.[14][15] 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.[16] However, sexual relations with a first-degree relative
(meaning a parent, sibling, or child) are almost universally forbidden.[17]
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 (preserved throughout the Middle English period)[18] and in the
narrow modern sense. The derived adjective incestuous appears in the 16th century.
[19]
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. Terms
like incester[20][21][22] and incestual[23][24] 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.[25]
History
[edit]
Antiquity
[edit]
In ancient China, 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).[26]
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.[27] According to Herodotus, Shah Cambyses II supposedly married two of his
sisters, Atossa and Roxane.[28][27] 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.[27] 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.[27]
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. [29][30]
[31][32]
However, it has also been argued that the available evidence does not support the
view that such relations were common.[33][34][35]
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. [36] 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, 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.[38]
Incest is mentioned and condemned in Virgil's Aeneid Book VI:[39] hic thalamum invasit
natae vetitosque hymenaeos – "This one invaded a daughter's room and a forbidden
sex act".
