We are more than just human biology. A vast chunk of our bodies are comprised of various “microbiomes” – little diverse bacterial worlds that co-exist, harm, or help us out, often without us realizing. From infection-fighting eyeball microbes to mood-influencing bacteria hiding in your digestive tract, they have a powerful influence over our daily lives – even if the underlying mechanisms remain unclear.

A new study, published in Biological Psychiatry, has investigated this link in human infants. Specifically, the team at the University of Carolina’s (UNC) School of Medicine wanted to know if you could associate a baby’s gut microbiome to their cognitive abilities in the near-future.

Sampling plenty of smelly stool samples from 89 1-year-olds, they profiled the species and types of bacteria found within. The samples were clustered into three different groups: one with high levels of the Bacteroides genus, one with high levels of the Faecalibacterium genus, and one with high levels of an as-of-yet unnamed genus in the family Ruminococcacaea.

Then, a year later, they gave these younglings a basic cognitive test to determine roughly how smart they were. They used the Mullen Scales of Early Learning, a range of tests that probe motor skills, the ability to perceive things, and crude language development.

By a significant margin, those in the Bacteroides cluster scored higher on the Mullen Scales tests than those in the other two clusters. Those belonging to the Faecalibacterium genus scored lowest.

Additionally, those with less diverse gut microbiomes outperformed those that had more diverse bacterial worlds swimming in their poop.

Babies make great detectives, but they do get tired out quite quickly. Aksana Tsishyna/Shutterstock

“We had originally predicted that children with highly diverse microbiomes would perform better,” coordinating author Rebecca Knickmeyer, associate professor of psychiatry at UNC’s School of Medicine, said in a statement. After all, she adds, “other studies have shown that low diversity in infancy is associated with negative health outcomes, including type 1 diabetes and asthma.”

It’s noted by the team that these different poop clusters seemed to be linked to a few external factors, including the parents’ ethnicities, having older siblings, duration of breastfeeding, and how exactly the baby was born.

The links between these factors and the types of microbiomes observed in the babies remain elusive, as do the causal mechanisms between the microbiomes and the cognitive aptitudes of the subjects. At this point, no one knows exactly what the bacteria are “doing” in order to influence the brain in this way.

It’s worth pointing out that 89 subjects is a small sample size and more work needs to be done to bolster the findings of the paper. Still, this adds credence to the idea that our minds are not entirely our own, and this planet, when it comes down to it, is a microbes’ world.