Why do humans have large brains? Scientists credit gut bacteria

Would you believe that your brain size is based on your gut bacteria? Weird right? The idea that gut bacteria have an influence on the evolution of human brain size is very intriguing and this hypothesis has now brought together neuroscience and microbiology denoting the evolution in biology.
The gut and brain are connected to an axis and it contains the vagus nerves, immune signaling neurotransmitters. The bacteria produced in the gut passes through these lines and it helps in influencing brain development and function. The gut bacteria produces metabolites and short-chain fatty acids that help in size development.

A research discovery from Northwestern University shared the evidence of how much the smallest element – gut bacteria – has played a role in the development of the human brain. The study published in the journal

Microbial Genomics

shares a new perspective on the long-standing evolution puzzle.

It was earlier discovered that microbes in the large intestine can produce compounds that can result in insulin resistance or weight gain, but it was never in the books that gut bacteria promoted the growth of the brain. Professor Katherine Amato, the study’s first author in a statement explained that the research study experimented using three primate species – humans. Macaques and squirrel monkeys with distinct brain sizes relative to their body mass.

The study was conducted in such a way that the gut bacteria from all three species were transferred into germ-free mice that were raised in sterile conditions.
For over 60 days, the experiment went on as they tracked multiple metabolic indicators, weight, food intake, body composition, and more. The study revealed the metabolic differences in mice receiving gut bacteria from humans who had higher food consumption but lower weight gain, and higher blood glucose, and these mice also had high levels of specific bacterial metabolites -SCFAa which are known to influence metabolism. And it was all in contrast to the mice that had the gut bacteria from macaque which stored more energy as fat despite eating less.

This research indicates that gut bacteria might help metabolic patterns and it favours the brain energy. However, as the study was limited to conditions, more research exploration to get a detailed abstraction on understanding human evolution is required.