Different epochs have often focused on quite different issues concerning incest, and they have frequently developed peculiar “obsessions” about particular pairs. During the seventeenth century, thousands of pages were written about incestuous relations between in-laws and step relatives, with a particular emphasis on the deceased wife’s sister, a relationship that scarcely counts as incest in the modern period. The particular threat of different violations needs to be understood in terms of the constant reconfiguration of kinship relationships. For example, the rise of cousin marriages from the middle of the eighteenth century throughout Europe provided the context in which the social imaginary played with incestuous bonding among siblings. But the representation of kinship relationships itself has not been a constant. In the seventeenth century, unlike in the Middle Ages, kin were thought of as connected through blood--and curiously enough allied kin could be seen as consanguines. In twentieth-century post-war Europe, the relationships among family members were more often represented as power relationships than anything else. Most recently, in popular culture the buzzword is “genetic sexual attraction.” Finally, the discourse itself continually changes. If in the seventeenth century, incest was discussed practically only as an issue of law--law as commandment--by the mid eighteenth century, it found a new language in “moral sentimentality. Not until the second half of the nineteenth century was incest seen through the lens of biology and the consequences for progeny. Post-war discussions were primarily couched in terms of psychotherapy, only to be supplanted in the past decade and a half by evolutionary biology.