Incest was regarded as a deadly sin
and taboo even in pre-social times when religion had not yet become a social
force. Incest refers to sexual activity within relatives, including family,
and, as the name suggests, it results in a kind of infection of the bloodline.
The infection is not specifically transmitted by any disease, but the genetic
damage that the offspring will suffer. The direct consequence of this is the
rapid degeneration of the bloodline, which endangers the survival, the
longevity of society, making this sexual activity much to be avoided or a great
crime. The best example of the degeneration is in the history when royal and
aristocratic families would get married within the noble family to preserve
bloodline, and as a result, whole royal families died away due to health
problems caused by some genetic disorder that got just worsened in the course
of time.
