According to Goldstein, the entire family structure and marriage system were subordinated to serve the land and corporate family unit.The family structure and marriage system of tre-ba were characterized by two fundamental principles: A "stem family" is one in which a married child is inextricably linked to his natal family in a common household.Polyandry is a marital arrangement in which a woman has several husbands.In Tibet, those husbands are often brothers; "fraternal polyandry".Bi-fraternal polyandrous marriages were more common than tri-fraternal or quadri-fraternal polyandry, because the latter forms of marriage were often characterized by severe familial tensions (reference missing).
Carbon-14 makes up about 1 part per trillion of the carbon atoms around us, and this proportion remains roughly constant due to continual production of carbon-14 from cosmic rays.
Historically the social system compelled marriage within a social class.
When the People's Republic of China annexed Tibet, political systems in many regions of Tibet remained unchanged until, between 19, political reforms changed the land ownership and taxation systems.
Another kind of marriage, although uncommon, is the "polygynous marriage".
In a family where all the children were female, sisterly polygynous marriage represented the most common choice.
In Goldstein's research about the Gyantse district specifically, he found them owning typically from 20 acres (81,000 m) of land each.