Chimpanzees who join in on more social activities have a higher diversity of microbes in their gut, and this microscopic species diversity might help fight diseases. The findings, published in Science Advances this week, suggests that social behavior shapes the microbiome and preserves diversity across evolutionary timescales. 

Sociality fuels the spread of pathogens among animal hosts (a crowded plane during the holidays, for example), but these sorts of interactions could also enable beneficial microbial associations. In humans and other primates, the gut microbiome in particular helps regulate health by training the immune system, metabolizing molecules and synthesizing nutrients, and generally protecting against infections caused by opportunistic pathogens. 

To evaluate the role of host social behavior in shaping gut microbial communities, a team led by UT Austin’s Howard Ochman coupled more than eight years of behavioral observations on chimpanzees at Gombe National Park in Tanzania with deep-sequencing of their resident bacterial communities. Between November 2000 and December 2008, 96 fecal samples were collected from 40 Kasekela individuals, including infants, juveniles, adolescents, adults, and elderly individuals. Chimpanzee sociability was calculated as the proportion of time individuals spent together on average. 

The team found that social behavior influences the richness of bacterial species that populate the gut. Chimpanzee sociability isn’t linked to the relative abundance, presence, or absence of any specific bacteria. The impact is on species diversity, which might be providing protection against pathogens that individuals with low species richness are missing. In humans, for example, low gut microbe species richness has been linked to Crohn’s disease.

Social behaviors propagate microbial diversity both within and between host generations. While infants inherit their gut microbial communities from their mother initially, the inheritance of these communities across generations is mostly influenced by social interactions with other chimpanzees.

While there are major differences between our social structures and theirs, the researchers think these results reveal the need to explore the links between human social networks and microbiome composition too.