Final answer:
Engels claimed that men's desire to control their property led to the establishment of monogamous marriage, which is an idea rooted in conflict theory that he developed with Marx. They viewed society as a battleground for resource competition among different social groups, notably between the bourgeoisie (owners) and the proletariat (workers).
Step-by-step explanation:
Friedrich Engels, a conflict theorist alongside Karl Marx, believed that the drive to control property led to certain social structures, including the institution of marriage. Specifically, Engels posited that men's desire to control their property brought about monogamous marriage. The reasoning was to ensure the legitimacy of heirs, linking marriage to the economic and class structures of society. Engels, together with Marx, also theorized about how the capitalist system breeds conflict between social classes, ultimately leading to societal changes.
Conflict theory, as conceived by Marx and Engels, is centered around the idea that social life is a competition, and subsequently society is marked by inequalities that generate conflict, rather than harmony and cohesion. Marx and Engels saw the capitalist system as inherently flawed, leading to exploitation and social strife, particularly between the bourgeoisie and the proletariat.