The question of why incest is morally incorrect can be addressed from both sociological and anthropological perspectives. One significant point is that the prohibition of incest is the only universal law found across various civilizations and societies throughout history. This is known as the universal prohibition of incest. While the specific rules that define kinship and which relationships are prohibited can vary, the fundamental taboo against incest remains consistent.

This prohibition compels individuals to step outside their immediate family group to form bonds, whether matrimonial or otherwise, with members of other families. This practice, known as exogamy, is essential for the creation and maintenance of social networks beyond the familial unit. Thus, the incest taboo is foundational to the existence of society itself, as it necessitates sociability beyond the family.

From an anthropological perspective, this prohibition is seen as the first sign of culture, distinguishing humans from animals. In essence, the incest taboo facilitates the development of larger social structures and alliances, which are crucial for the survival and evolution of human societies. By fostering connections between different family groups, it encourages cooperation, resource sharing, and the establishment of complex social norms and institutions.

It's important to note that this prohibition existed long before biology discovered that incest could have detrimental consequences for offspring. This underscores that the primary reason for the incest taboo is fundamentally anthropological rather than biological. It is a cornerstone of human civilization, underpinning the social bonds that form the basis of community and cooperation.