Final answer:
Incest was often a royal prerogative in ancient Egypt and among Hellenistic kingdoms to preserve divine bloodlines or secure political alliances. Despite the wide prevalence of the incest taboo, definitions varied, and incest was sometimes sanctioned within royal families to maintain purity and power.
Step-by-step explanation:
In certain historical contexts, incest was seen as a prerogative for royalty, with one of the most notable examples being ancient Egypt. The pharaohs often married within their family to preserve the sanctity of their divine bloodline. Unfortunately, this practice led to health and mental issues due to inbreeding. However, the day-to-day governance was handled by a skilled and well-established bureaucracy, which cushioned the state from the negative effects of an inbred monarchy.
In other parts of the ancient world, dynastic marriages, including those that would be considered incestuous, were instrumental in securing peace treaties and alliances. For instance, in the Hellenistic kingdoms such as Egypt under the Ptolemies or the Seleucid Empire, marrying siblings or close relatives could be part of political strategy.
The incest taboo is almost universal across cultures, but the definition of what constitutes incest has varied widely. In many societies, the incest taboo does extend to other relations considered too close for sexual relationships. Yet, incest in royal lineages was sometimes deemed acceptable or even necessary for maintaining the purity of lineage and consolidating power.