How does social complexity shape brain structure, its metabolic costs, and the behavioral capability of individuals? The Social Brain Hypothesis posits that larger groups require bigger brains to adaptively process social information, while the Expensive Tissue Hypothesis considers the cost of producing them. Social insects—ants, bees, termites and wasps—live in groups ranging from tens to millions of individuals, have miniaturized brains that support striking individual cognitive abilities and are renowned for their remarkable collective intelligence and division of labor. The distributed processing of information by task-specialized workers might relax the cognitive challenges of individuals, leading to a reduction in brain investment. Additionally, energetic expenses associated with brain size are not well understood in any clade.
Human societies are also characterized by division of labor and collective intelligence. However, it is difficult to examine how social life influenced our brain evolution: we are a single species and historical analyses are limited to comparison of cranial capacity of fossil forms. Ants, in contrast, are a species-rich clade that shows broad variation in social complexity and body size, enabling phylogenetic and socioecological contrasts. Our research can help identifying general principles of the evolutionary neurobiology of social animals, including us. The miniaturized ant brains can inform about evolutionary trade-offs, and how selection for neural efficient and minimal neuroarchitectures can solve cognitive problems and support social behavior. Research on ants has additional societal benefits, for example, by inspiring computer scientists to develop distributed computing systems or inexpensive robots exhibiting swarm intelligence.
We aimed to understand the relationship between brain size, region investment, metabolic costs and individual cognitive abilities of ant workers under different levels of sociality. We examined the effect of distributed information processing, worker polymorphism and colony size on the neurobiological, cognitive and behavioral characteristics of ant workers, and on investment in functionally specialized brain compartments that underlie behavior. To do so, we applied collective animal behavior approaches and tools and neurobiological methods.
We have described anatomical and physiological differences among brains of ant species varying in their social organization and brains of ants from the same colony that perform different social roles. We have also developed technical innovations in brain imaging and brain metabolism to study ant brains. We are designing a learning device that will allow inter and intra species comparisons. This action has strengthened and broadened the research skills and collaboration network of the MSCA fellow, allowing her to find an independent position in Spain.
