Final answer:
Fraternal polyandry is practiced in certain Tibetan societies where brothers share a wife, which aids in preserving family land and minimizing population growth. Polygyny is globally more common, but fraternal polyandry is particularly notable in Tibetan societies. While monogamous relationships are also found, especially in urban and Christian communities, polygamous arrangements exist with varying levels of acceptance and practice.
Step-by-step explanation:
The question 'When brothers share a wife, what marriages are the most common in Tibetan society?' refers to the practice of fraternal polyandry which is quite rare but has been known to occur in certain societies like in Nepal and, historically, in parts of Tibet. In this form of marriage, brothers share one wife, which has certain social and economic benefits, especially in areas where resources and land are scarce. Rather than dividing inherited property, brothers maintain family unity and land integrity by marrying the same woman. This form of polyandry also helps in minimizing population growth in densely populated areas with limited resources.
In terms of polygamous marriages, while polygyny is more common globally - where one man marries multiple women - fraternal polyandry is the most notable in the Tibetan context when brothers share a wife. This type of marriage arrangement can help maintain economical stability and sustain agricultural practices in challenging environmental conditions.
Polygamy is accepted in many societies, but it is not universally practiced, with figures indicating that only a small percentage of the population engages in such relationships. Monogamous relationships are also present, especially in urban and Christian areas, as evidenced in regions like Burundi and among contemporary urban societies, where they are considered standard.