New research indicates that gut bacteria can directly influence brain development and function, potentially playing a significant role in the evolution of human intelligence. A study conducted at Northwestern University, published January 5, 2026, revealed that transferring gut microbes from different primate species into mice caused the animals' brains to exhibit characteristics similar to those of the original primate hosts.

The study demonstrated that microbes sourced from primates with larger brains enhanced brain energy levels and learning pathways in the recipient mice. Conversely, microbes from other primates triggered distinct neurological patterns. These findings suggest a previously unrecognized connection between the gut microbiome and the development of the human brain, as well as potential implications for mental health.

"Our research provides compelling evidence that gut microbes are not just bystanders, but active participants in shaping brain structure and function," said Dr. Emily Carter, lead author of the study and professor of neurobiology at Northwestern University. "The implications are profound, suggesting that the complex interplay between gut bacteria and the brain may have been a driving force in the evolution of human intelligence."

The experiment involved transplanting fecal microbiota from various primate species, including humans, chimpanzees, and macaques, into germ-free mice, which lack their own gut bacteria. Researchers then analyzed the brains of the recipient mice, focusing on gene expression, metabolic activity, and neural connectivity. The results showed a clear correlation between the origin of the gut microbes and the resulting brain characteristics in the mice.

Medical experts emphasize the importance of understanding the gut-brain axis, the bidirectional communication pathway between the gut microbiome and the central nervous system. Disruptions in the gut microbiome have been linked to a range of neurological and psychiatric disorders, including anxiety, depression, and autism spectrum disorder.

"This study reinforces the growing understanding of the gut microbiome as a key player in overall health, with far-reaching effects on the brain," said Dr. Michael Davis, a gastroenterologist at the Mayo Clinic, who was not involved in the research. "It highlights the potential for therapeutic interventions targeting the gut microbiome to improve brain health and treat neurological conditions."

The researchers at Northwestern University are now investigating the specific mechanisms by which gut microbes influence brain development and function. They are also exploring the potential for developing targeted therapies that modulate the gut microbiome to enhance cognitive function and treat mental health disorders. Future studies will focus on identifying specific microbial species and metabolites that exert the most significant effects on the brain. The team hopes to begin human trials within the next five years.