Final answer:
Engels claimed that men's desire to control their property led to the establishment of monogamous marriage, reflecting the conflict between property owners and the proletariat within capitalist societies.
Step-by-step explanation:
Friedrich Engels, a notable conflict theorist, posited that the patriarchal desire to control property brought about significant changes in familial and gender relations. One of the key social transformations Engels attributed to this drive was the establishment of monogamous marriage. He argued that, within a capitalist society, men sought to ensure the transmission of their property to their own offspring, thereby solidifying the institution of monogamous marriage. This was also tied to the broader context of social and class struggles during the industrial era where the bourgeoisie sought to assert control over their assets and maintain social dominance over the proletariat.