Social behavior and the microbiome

INSIGHT METAGENOMICS Social behavior and the microbiome Social interactions influence the communities of microbes that live in wild baboons. predict gut microbiome composition in wild baboons. eLife 4:e05224. W hy did social interactions evolve? Complex rules govern how we interact when we meet, and while these principles are often bewildering, they are also somehow intrinsic to the fabric of any human society. Now, in eLife, Elizabeth Archie, Jenny Tung and co-workers have provided compelling evidence to support the theory that physical interaction evolved in vertebrates to help share potentially health-promoting bacteria (Tung et al., 2015). Tung et al. sequenced the genomes of the various microbes found in the faeces of 48 baboons from two different social groups in Amboseli in Kenya. They found that these 'microbiomes' differed between the two social groups, despite them living in overlapping areas and eating similar foods. It has been shown that diet influences the composition and structure of the microbial communities living in the human gut (David et al., 2013). So why were the microbiomes of these groups of baboons not more similar? The answer lies in the fact that baboons interact by grooming each other (Figure 1). Baboons that groomed each other more frequently had more similar microbiomes, which suggests that physical interactions with others are very important in shaping the microbial communities in these individuals. Baboons don't tend to groom baboons from different social groups (much like humans), so social activities within a group act to consolidate shared communities of microbes. The need for physical interaction or the presence of others is central to human cognitive psychology. Embodied cognition is the study of how the presence of others affects thoughts, feelings, and behaviors (Meier et al., 2012); for example, we tend to distance ourselves physically from those we don't like or trust, whereas we tend to be more physically close and have more physical interactions with our friends and family. It is highly probable that evolution has shaped social behavior. Physical interactions with those we love feels good; hugs, kisses, and even basic skin-to-skin contact have positive influences on our thoughts and feelings. The hand-shake—which is the standard mode of introduction in many societies—represents this concept. But why did these interactions evolve? Are they purely social constructs, or is physical interaction instinctive, driven by some selective advantage? Sharing microbes in this way can be beneficial: for example, bumblebees living in the same …