The multiple definitions of incest

In early modern Sweden, a widower and his late wife's sister could be sentenced to death by beheading if it was established that they had had sexual intercourse with each other. The relationship was defined as incestuous, and neither could expect to be pardoned unless there were significant mitigating circumstances. Since then the definition of incest has changed considerably, and sexual relationships between in-laws are no longer considered to be a criminal act: modern Swedish law only defines sexual relationships within the nuclear family as incestuous (parent/child or brother/sister). Over the last 300 years, Swedish legislation concerning incestuous relationships – and legal praxis – has thus changed from being one of the strictest in Europe to being one of the most liberal.

Sexual relationships between close kin have been restricted by law or custom in most societies and cultures. Nevertheless, the forms and the consequences of the regulations have varied considerably depending on the place and period in question. For example, in ancient Egypt and Persia, marriages between members of the nuclear family were accepted – relationships that have been strictly forbidden in most other cultures. In northern India the attitude towards marriage between family members has been quite strict, while the culture of southern India has encouraged marriages between first cousins, for example, or between uncles and nieces. In the Middle East, marriages between first cousins whose parents were brothers were considered to be particularly beneficial liaisons, while in Korea and China marriages between first cousins were allowed only if the parents were not brothers (namely if the parents were two sisters or a brother and a sister). The rules have hence changed both between different cultures and within one culture over time.

These substantial variations in regulation are a strong indication that incest taboos are to some extent socially constructed. At the point when a country's prohibitions are set, lawyers and legislators are inevitably influenced by their cultural context – and when there is a change in values and ideological ideas in a society, attitudes towards incestuous relationships change too.