Explanation:
1. Lineage Exogamy.
Members of the same localized lineage are forbidden from marrying. Exogamy and incest prohibitions among agnates (patrilineal relatives) mark the patrilineages as a significant units in the mutual exchange of marriage partners and in the consequent formation of alliances.
2. Bilateral Cross Cousin Marriage.
The Yanomamo follow a bilateral cross-cousin marriage system whereby marriage partners are doubly related to one another as matrilateral and patrilateral cross cousins as a consequence of similar marriages among their parents.
Bilateral cross cousin marriage
In each generation a man marries a woman who is both his
MBD (matrilateral cross cousin) and FSD (patrilateral cross cousin)
This arrangement creates a situation in which pairs of exogamous lineages are continually allied through the exchange of women. Among the Yanomamo these intermarring groups co-reside in and form the core of village settlements and thereby assume the form of moieties.
(See the unit on cross cousin marriage for a fuller demonstration of bilateral patterns.)
3. Village endogamy.
The bilateral cross cousin marriage system and co-settlement of intermarrying lineages establishes a pattern of village endogamy . This pattern is variable, however, since conditions of warfare create the need to form marriage alliances outside of the immediate settlement. Accordingly, the rate of endogamy varies with village size and power. Larger groups have less need for outside alliances and can maintain high levels of endogamy. Smaller, weaker units, must limit inmarriage and provide brides to neighbouring settlements in return for military support. Chagnon demonstrates this pattern in two villages:
Patanowa-teri is a large village of 212 residents and has an endogamy rate of 85% of all marriages.
Lower Bisaasi-teri has a population of only 51 and an endogamy rate of 50%.
(You may want to observe a similar situation for Turkish peasant endogamy, but note that the measures of endogamy in the two studies differ.)
4. Polygyny
The Yanomamo follow a practice whereby men can and normally do marry more than one wife as a benefit and marker of social status. Polygyny of this sort is sometimes explained as a result of male and female demographic imbalances, but the Yanomamo have significant more men than women in their populations because of female infanticide. Polygyny is possible in such a situation only if some men do not marry or, more usually, if they marry at a much later age than women do.
