Human Amygdala Volumetric Patterns Convergently Evolved in Cooperatively Breeding and Domesticated Species

Area of Science:

• Neuroscience
• Evolutionary Biology
• Comparative Anatomy

Background:

• The amygdala, particularly its lateral nucleus, plays a vital role in social behavior and fear processing.
• Humans exhibit a disproportionately larger lateral amygdala nucleus compared to other apes.
• This finding aligns with hypotheses of human evolution, including self-domestication and cooperative breeding.

Purpose of the Study:

• To investigate the evolutionary origins of the enlarged lateral amygdala nucleus in humans.
• To explore the role of convergent evolution in the development of this brain region across species.

Main Methods:

• Phylogenetic analysis was conducted on a sample of 17 mammalian species.
• Single amygdala nuclei volumetric data were acquired for each species.

Main Results:

• Convergent evolution toward larger lateral amygdala nuclei was observed in both domesticated and cooperatively breeding mammals.
• Reduced fear-induced aggression, through altered processing of fearful stimuli, appears to be a shared neurobiological mechanism.

Conclusions:

• The findings suggest that selection pressures for reduced fear aggression are linked to the enlargement of the lateral amygdala.
• While both domestication and cooperative breeding involve reduced aggression, cooperative breeding is more strongly associated with the enhanced proactive prosociality seen in humans.