Avunculate marriage

Avunculate marriage is marriage between an uncle and a niece or between an aunt and a nephew (second-degree relative). In some societies avunculate marriage is prohibited as a form of incest, while in others it is legal, even common.

The partners of an avunculate marriage have the same genetic relationship as half-siblings or a grandparent and grandchild, sharing on average 25% of their genetic material. This is more than that of a first cousin relationship, in which on average the members share 12.5% of their genetic material, but less than that of cousin-siblings (37.5%) or full siblings (50%).

Avunculate marriages were once frequent among the royal houses of Europe, as Leviticus 18 was not interpreted to explicitly forbid the marriage of a man with the daughter of his sibling; in Catholic countries a papal dispensation could be and often was obtained to allow such a marriage. According to the Talmud, avunculate marriage (specifically an uncle marrying his niece) is commended by Jewish law, however, Sadducees and other Jewish sects believed that such unions are Biblically prohibited. Avunculate marriage is banned in Islam, thus it is illegal in most Muslim countries. Avunculate marriage is currently illegal in most Anglophone jurisdictions, but is allowed in Argentina, Australia,Austria, Brazil, France, Finland,Malaysia,The Netherlands, and Russia. Avunculate marriage is the preferred type of union among the Awá-Guajá people of the eastern Amazon basin.

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