Final answer:
Polygyny in human history is associated with genetic diversity and status, maximizing labor and resources in a family unit. Monogamy is thought to have evolved through mechanisms that ensure mutual parental investment and reduce competition for mates. Both forms of marriage are influenced by cultural, economic, and evolutionary factors.
Step-by-step explanation:
In evolutionary biology, the hypotheses for why polygyny has been a common form of marriage throughout human history include its advantages in increasing genetic diversity and social status. Polygyny, or one man marrying multiple women, is often associated with maximizing family labor and resources, as well as creating strong kinship networks, resulting in higher social status and political power. It's found in cultures where child labor is beneficial to food production and is often practiced when women have territories rich in resources, attracting multiple males.
On the other hand, the cultural shift towards monogamy, where one male pairs with one female, can be understood through hypotheses such as the "mate-guarding hypothesis" where males prevent other males from mating with their female, the "male-assistance hypothesis" where males aid in offspring rearing leading to healthier offspring, and the "female-enforcement hypothesis" where females ensure that males invest resources only in her offspring. In postindustrial societies, monogamy is adapted to highly mobile family units and encompasses same-sex marriage.
In summary, the evolution of monogamy may be influenced by enhanced parental investment by both parents and reduced intrasexual competition, while polygyny may offer survival advantages through efficient resource distribution and cooperation among family members.