Incest

Incest means sexual intercourse between people who are closely related. Usually, this means members of the same family. In many societies, it is forbidden by law and religion. Which relatives it is forbidden to have sex with depends on the law, religion and culture.

Incest is now regarded as bad for the genetic health of the offspring, and it is often forbidden by present-day religions and laws.^[1][2] The fundamental reason has to do with genetics. Incestual societies will have a high rate of birth defects, significant enough for it to be noticed even when little was known about the cause. To some extent this is a surmise, because ancient societies had no knowledge of genetics as such. But they must have noticed some connection between birth defects and the relationship between parents. We think this because widespread bans on closely related persons marrying came long before the understanding of modern genetics.

In history (as far as we know it) there were societies which allowed incestual marriages and individual acts of incest. Famously, the ancient Egyptian royal family practised incest, though not exclusively. It is thought that the frequency of early non-trauma deaths (such as Tutankhamun) was due to the effect of incest. We do know that incest was practised in their royal family. Cleopatra was married to her brothers, Ptolemy XIII and Ptolemy XIV. Roman records show that marriages between close siblings were common in Ancient Egypt.^[3][4]

So, if pregnancy is a risk, there is a reason based on health. Children that result from incest between blood relatives are more likely to have birth defects.

1. ↑ Levesque, Roger J.R. 1999. Sexual abuse of children: a human rights perspective. Indiana University Press. pp. 1, 5–6, 176–180. ISBN 9780253334718
2. ↑ United Nations Convention on the Rights of the Child. 1989. Office of the United Nations High Commissioner for Human Rights.
3. ↑ Brent D. Shaw: Explaining Incest: Brother-Sister Marriage in Graeco-Roman Egypt. In: Man. New Series, Volume 27, Royal Anthropological Institute of Great Britain and Ireland, London 1992, pp. 267–299
4. ↑ Keith Hopkins: Brother-Sister Marriage in Roman Egypt. In: Comparative Studies in Society and History. Volume 22, Issue 3, Society for Comparative Studies in Society and History, London New York Juli 1980, pp. 303–354 (doi:10.1017/S0010417500009385). also see: Sofie Remijsen, Willy Clarysse: Incest or Adoption? Brother-Sister Marriage in Roman Egypt Revisited. (PDF; 86 kB; 8 Seiten) In: JRS 98 (2008), pp. 53–61. Leuwen 2008 accessed 8th of July 2013).