The Microbiome & Behavior Project is a multi-disciplinary research project that I co-direct with Athena Atkipis, in my role as a postdoc within the Aktipis Cooperation and Conflict Lab at ASU. More details on this exciting new initiative can be found here on the Psych Dept website (scroll down for M&BP).
Gut microbes have the capacity to affect human mental health, cognitive functioning, and behavior. As detailed in the figure below, from this 2014 paper written by collaborators Joe Alcock, Athena Aktipis, and Carlo Maley, gut flora have access to important regulators of human eating behavior. Given that diet is a fundamental component of gastrointestinal microbiome composition, selection would be expected to favor microbial variants that increase their hosts' intake of preferred foods. Our current studies examine oral microbiome and sugar intake, and restrictive eating and gut microbiome.
Like other organisms, symbiotic microorganisms must solve the adaptive problem of access to resources. All of the microbes in and on our bodies are acquired from environmental and host-associated microbes, through a process of horizontal transmission. The human microbiome habitat is contained within an organism that is itself subject to selection at the individual level, operating by vertical transmission of genetic material from parent to offspring. In this microbial world, hosts should evolve traits to minimize harm from pathogenic strains, and maximize the benefits derived from commensals. Yet, horizontal transmission feasibility decouples microbial fitness from that of the current host, and is associated with the evolution of virulence. Access to host-associated resources and dependency on hosts for survival, in contrast, aligns fitness interests between microbial strains and their host organism. Food is one such resource. Joe Alcock, Athena Aktipis, and I discuss some of these ideas in a recent paper that appeared in the Annals of the New York Academy of Sciences.
For sociality to evolve, from an ancestral, solitary lifestyle, benefits need to have exceeded costs; pathogen exposure is one such tradeoff for social interaction. However, social interaction exposes animals to commensal microorganisms as well as pathogens, though this important benefit of sociality is often overlooked (See this 2008 paper by Michael Lombardo for a convincing argument that exchange of commensals was one of the benefits that favored the evolution of sociality). One of our project themes is the exploration of social behavior, in particular food sharing behavior, and the exchange of beneficial commensals. We are currently collecting experimental data about the effects of food sharing on cooperative behavior.