A Band of Brothers-In-Law

A study from the University of Utah has revealed important differences between the fighting behaviour of apes and small groups of humans. Chimpanzees are the only species of ape who fight as groups, like humans, and so it has been long theorised that they might fight in similar ways to us. However, while chimpanzees fight in groups of closely related kin, or as  “bands of brothers”, recent anthropological work on the Yanomamö men in the Amazon reveals a different, more social pattern of fighting behaviour.  Researchers Shane Macfarlan and Napoleon Chagnon discovered that these men formed alliances with similarly-aged men from other villages to attack other communities. Rather than individual villages fighting each other, these men fight alongside each other against common enemies.

Macfarlan states that the fighting groups of Yanamamö men might rightly be called “bands of brothers-in-law” due to the commonly-observed practice of marrying the sisters and cousins of their allies-in-arms. Not only do these men fight together, but their alliances are strengthened by social and political ties, showing a far more complex structure than that of the fighting groups of chimpanzees. Given the complexity of human interactions compared to those of apes, this may seem unsurprising. But the fact that these men fight not in familial, but in social groups is  nonetheless anthropologically significant.

The study is shrouded in controversy, with its lead anthropologist, Chagnon, having been heavily criticised in the past for an over-reliance on biological and genetic explanations for human behaviour. However, Macfarlan contends that Chagnon has, in reality, taken a balanced view. Biology is necessarily important in anthropological study, and, in combination with social observation and theory, it allows for a holistic approach to the understanding of human behaviour. The elevation of Macfarlan to the National Academy of Sciences should perhaps be seen as validation for this interdisciplinary approach.