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 by researchers 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 host species.

The findings suggest that gut microbes may have contributed to the development of large, energy-intensive brains in primates, including humans. According to the study, microbes sourced from primates with larger brains enhanced brain energy levels and strengthened learning pathways in the recipient mice. Conversely, microbes from other primates triggered distinctly different brain activity patterns.

"Our research demonstrates a clear link between the gut microbiome and brain function," said Dr. Emily Carter, lead author of the study and professor of neurobiology at Northwestern University. "The implications are profound, suggesting that the microbes residing in our gut may have been a crucial, yet previously unrecognized, factor in shaping the human brain."

The study involved transplanting fecal microbiota from various primate species into germ-free mice, which lack their own gut bacteria. Researchers then analyzed the mice's brain activity, gene expression, and cognitive performance. The results consistently showed that the mice's brains mirrored certain characteristics of the primate species from which they received the microbes.

The medical context of this research lies in the growing understanding of the gut-brain axis, a bidirectional communication pathway between the gut microbiome and the brain. Disruptions in the gut microbiome have been linked to various neurological and psychiatric disorders, including anxiety, depression, and autism spectrum disorder.

"This research provides further evidence for the critical role of the gut microbiome in overall health, including mental health," stated Dr. David Miller, a gastroenterologist at the Mayo Clinic, who was not involved in the study. "It highlights the potential for therapeutic interventions targeting the gut microbiome to improve brain function and treat neurological conditions."

The practical implications of this research for readers include the importance of maintaining a healthy gut microbiome through diet and lifestyle choices. A diet rich in fiber, fruits, and vegetables can promote the growth of beneficial gut bacteria. Probiotic supplements may also be beneficial, although more research is needed to determine the optimal strains and dosages.

"While we are still in the early stages of understanding the complex interactions between the gut microbiome and the brain, this study offers a compelling glimpse into the potential for manipulating the microbiome to enhance cognitive function and treat neurological disorders," Dr. Carter said.

Future research will focus on identifying the specific microbial species and metabolites responsible for the observed effects on brain function. Researchers also plan to investigate the potential for developing targeted therapies that can modulate the gut microbiome to improve brain health.