Behave: The Biology of Humans at Our Best and Worst

Hierarchy is “a ranking system that formalizes unequal access to limited resources, ranging from meat to that nebulous thing called ‘prestige’” (426). Many but not all species have hierarchies. Hierarchies work to establish status quos, which avoids conflict. The benefits of hierarchy are individualistic: Superiors benefit via access to resources, and subordinates benefit by avoiding being attacked by superiors.

Some highly social animals, such as primates and ravens, are able to recognize gradations of rank, i.e., an individual in rank 5 is above me, at rank 6, but below rank 4. Such social cognition is intellectually taxing, and as a general rule the larger an animal’s social group, the larger the brain and neocortex of the species relative to body size. Sociality is particularly complex in fission-fusion species, as the ranks of individuals can differ in subgroups vs. whole groups. As expected, primates from fission-fusion species have larger neocortices and are better at frontocortical tasks.

Rank and Hierarchy in Humans

Average stable human group size exists around 150. The larger the individual’s social group, the larger their vmPFC, orbital PFC, and amygdala, and the better they are at ToM skills. As humans belong to multiple groups, we also belong to multiple hierarchies.