Evidence for an Evolutionary Continuity in Social Dominance: Insights from Nonhuman Primate Tractography
J. Neurosci.. 2025-07-21; 45(33): e1646242025
DOI: 10.1523/jneurosci.1646-24.2025
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https://www.bordeaux-neurocampus.fr/11956
The dynamics of social dominance play a significant role in regulating access to resources and influencing reproductive success and survival in nonhuman primates. These dynamics are based on aggressive and submissive interactions that create distinct, hierarchically organized social structures. In humans, whose social behavior is similarly organized, the use of brain imaging based on tractography has identified key neuronal networks of the limbic system underlying social behavior. Among them, the uncinate fasciculus and the cingulum bundle have been associated with aggression and some disorders such as psychopathy. In this study, we have used advanced tractography to study the anatomy of connections underlying social dominance in a colony of 15 female squirrel monkeys (
Saimiri sciureus
). We correlated the biostructural properties of the uncinate fasciculus and cingulum with behavioral hierarchy measures while controlling for factors such as age, weight, handedness, brain size, and hormonal influences. The fornix, a limbic connection involved in memory, was also included as the control tract. Our findings indicate a significant correlation between the integrity of the right uncinate fasciculus and social dominance measures, including normalized David’s scores, aggressive behaviors, and submissive behaviors. Trends observed in the left uncinate fasciculus hint at potential bilateral involvement with a right hemispheric lateralization. These results are consistent with human studies linking the uncinate fasciculus to social aggression and disorders, suggesting an evolutionary continuity in the neuroanatomical substrates of social dominance back to at least 35 million years.