For this study, the researchers observed a community of 40 chimpanzees living in Tanzania's Gombe National Park over the course of eight years. The chimps' social calendar relies largely on the season—during the dry season, they spend most of their time alone, but in the wet season, they spend a lot of time with others while foraging for food. During different seasons and over the years, the researchers took a number of fecal samples and sequenced the genes of the bacteria inside.

They found that, when the chimps were spending more time together, no particular type of bacteria appeared more frequently, but overall their microbiomes had a greater diversity of species in them. During these social periods, the microbiomes between individuals were also more similar—to the researchers, this indicates that social interaction might be another way by which bacterial colonies are passed around and down through generations (researchers already knew that mothers pass on their microbiome to babies both before and after they're born, and can be affected by the medications and foods people consume). And while the chimps' similar food source might be responsible for some of that microbial similarity, social behaviors like grooming and poop flinging allow for transmission of good and bad bacteria as well.

The researchers still need to see whether the chimps' microbial diversity protects them from diseases, though previous studies indicate that it's likely. The team also hopes to test the relationship between the diversity of the microbiome and socialization in humans. If the relationship is the same, it could help researchers better understand intestinal conditions such as irritable bowel syndrome and Crohn's disease. It might also help scientists understand why people who are social live longer.