Final answer:
The Yanomamo form inter-village alliances that may include practices such as cousin marriage to maintain tribal blood percentage. Strategic marriages reinforce alliances, a common practice among various indigenous societies.
Step-by-step explanation:
The Yanomamo tribes, like many indigenous societies, form inter-village alliances that are often reinforced through marriage practices. While the provided references do not specifically discuss the Yanomamo, the notion of marshaling blood through cousin marriage is a concept observed in tribal communities as mentioned by Nenemay (2005). The policies of some tribes require individuals to establish descent from an enrolled member to claim tribal membership, and cousin marriage may be a strategic means to maintain blood quantum within the necessary thresholds.
Concerning the mechanics of forming alliances, anthropology literature suggests that such alliances are forged through a variety of means, including ceremonial exchanges, reciprocal gift-giving, and indeed, strategic marriages. The idea of reinforcing political and social ties through marriage is a widespread practice and can also be paralleled with other indigenous societies that perform similar kinship and marriage strategies for alliance-building purposes.