Inter-group Coalition Formation

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Human Uniqueness Compared to "Great Apes": 
Relative Difference
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As with intra-group coalitions, inter-group coalitions are groups that act cooperatively in competitive or aggressive contexts against another individual or unit. Inter-group coalitions represent the temporary union of two groups with weaker associations between than found within groups. Among humans they may be organized around kin, visiting and gift-giving, and co-participation in cultural activities such as rites of passage.



Timing of appearance of the difference in the Hominin Lineage as a defined date or a lineage separation event. The point in time associated with lineage separation events may change in the future as the scientific community agrees upon better time estimates. Lineage separation events are defined in 2017 as:

  • the Last Common Ancestor (LCA) of humans and old world monkeys was 25,000 - 30,000 thousand (25 - 30 million) years ago
  • the Last Common Ancestor (LCA) of humans and chimpanzees was 6,000 - 8,000 thousand (6 - 8 million) years ago
  • the emergence of the genus Homo was 2,000 thousand (2 million) years ago
  • the Last Common Ancestor (LCA) of humans and neanderthals was 500 thousand years ago
  • the common ancestor of modern humans was 100 - 300 thousand years ago

Possible Appearance: 
100 thousand years ago
Probable Appearance: 
400 thousand years ago
Background Information: 

 Inter-group coalitions have not been described for any primate other than humans. “Third-order” alliances among adult male bottlenose dolphins (Tursiops sp.) in Shark Bay, WA., are probably the best example of inter-group coalition formation among non-humans. In this population adult males organize into three levels of alliance formation, working together to capture and defend female mates from other males. While first- and second-order alliances both fall into the “intra-group alliance” category, third-order coalitions are temporarily formed of two second-order alliances working cooperatively in mate competition against other allied male groups. Inter-group coalitions also exist among elephants, at the level typically referred to as the “bond group.” The primary level of organization within elephant social groups is the “family unit”. “Bond groups” are comprised of 2-5 family groups who have been observed to ally against aggressors and defend one another in times of danger.The paucity of inter-group coalitions among primates despite years of observation suggests that this is likely a case of evolutionary convergence among three mammalian species demonstrating high degrees of social and cognitive complexity. However, it is also worth noting that the differences in social organization across taxa, as well as in characterizing the different levels of social organization, make cross-taxa particularly challenging for this topic. 

The Human Difference: 

Humans live in semi-closed social groups with bisexual philopatry and dispersal. In a single group, brothers and sisters may co-reside, though the trend tends toward male biased kinship groups with female dispersal. Flexible residence patterns mean that neither sex is surrounded by mostly kin. Drawing from Chapias (2008), Hill et al (ibid) hypothesize that “ monogamous pair bonding, paternal recognition within cooperatively breeding social units, and bisexual dispersal facilitate frequent and friendly intergroup relationships and migration and low group genetic relatedness of band co-residents.” As we will see, many of these variables are also at hand in human inter-group alliance formation.

Mechanisms Responsible for the Difference: 

Kinship is a critical variable in the formation and mediation of inter-group alliances among humans. Among the Yąnomamö, Chagnon (1968/2012) reported that the leader of a focal tribe had relatives both within and outside of his village. When kin do not exist, they are created through the exchange of women. Allies bound by affinial kinship ties are more interdependent because they are under obligation to each other to continue to this exchange. Among Eskimo nations, co-marriage, where two husband-wife pairs changed sexual partners on at least one occassion, or co-spousing between each man and the other’s wife, served as an important mechanism for establishing and maintaining alliances. Inter-group alliance are also established through trade. Among the Enga of Papua New Guinea, alliances are mediated during triennial Tee Ceremony Exchanges, which are both a show of strength and an opportunity to establish and maintain ties with other groups (Wiessner 2009). Trade partnerships are critical elements of alliance formation among Eskimo nations (Burch 1980), and are generally thought to function in maintaining military alliances. Among Enga, Yąnomamö, and Eskimo populations, feasts were noted as political events, critical in the mediation of inter-group alliances. Weissner (ibid) notes two other types of ceremonial exchange that mediate alliances among the Enga: Kepele ceremonies, which “drew together hundreds to thousands of participants to initiate boys, to express equality of male tribal members, to communicate with the ancestors, and to host guests from other tribes for massive feasts,” and Great ceremonial wars, “tournament fights fought recurrently between entire tribes or pairs of allied tribes to demonstrate strength and brew the grounds and spirit for the feasts and exchanges of enormous proportions.”

Possible Selection Processes Responsible for the Difference: 

Organization and function of inter-group are closely related where resources such as women and goods are exchanged. Alliances mitigate conflict between groups. Chagnon (ibid) noted that Yąnomamö tended to avoid attacking those villages with which they trade and feast, unless some specific incident (such as abduction of women), provokes them, and that allies linked by trade & feasting ties rarely accused each other of practicing harmful magic. Yąnomamö allies were under obligation to provide shelter and sustenance to each other whenever one of them was driven from his village and garden by a powerful enemy. Of Eskimo alliances, Burch (1980) wrote, “In times of peace they were the primary mechanism through which intersocietal trade was conducted, and they were the ultimate recourse when famine struck a region and its inhabitants fled to neighboring territories. In times of war they served to reduce the level of bloodshed. Even though partners and co-spouses might find themselves on opposite sides in armed conflict, they ordinarily would try to avoid direct confrontation…Alliances in short helped improve the quality of life in good times and helped increased survival rate in bad.” Perhaps the most critical role for alliances is to increase strength and size in the threat of hegemony. In Yąnomamö ideology strong villages should take advantage of weaker ones, therefore villages should create alliances and show strength; but are also inhibited by the same ideology that drives their creation. For Eskimo groups, alliances among similarly threatened neighbors worked together against powerful outsiders. For example in 1800 C.E. the Eskimo nation Tikiġaġmiut was threatening hegemony and was the only nation with enough people to do so. They were defeated by an alliance of 3-4 nations banned together.

Related MOCA Topics


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