Microbes can influence host physiology and behavior in many ways. Here we review evidence suggesting that some microbes can contribute to host stress (and other microbes can contribute to increased resilience to stress). We explain how certain microbes, which we call “stress microbes,” can potentially benefit evolutionarily from inducing stress in a host, gaining access to host resources that can help fuel rapid microbial replication by increasing glucose levels in the blood, increasing intestinal permeability, and suppressing the immune system. Other (...) microbes, which we term “resilience microbes,” can potentially benefit from making hosts more resilient to stress. We hypothesize that “stress microbes” use a fast life history strategy involving greater host exploitation while “resilience microbes” use a slow life history strategy characterized by more aligned evolutionary interests with the host. In this paper, we review the evidence that microbes affect host stress and explain the evolutionary pressures that could lead microbes to manipulate host stress, discuss the physiological mechanisms that are known to be involved in both stress and microbial activity, and provide some testable predictions that follow from this hypothesis. (shrink)

The presence of fetal cells has been associated with both positive and negative effects on maternal health. These paradoxical effects may be due to the fact that maternal and offspring fitness interests are aligned in certain domains and conflicting in others, which may have led to the evolution of fetal microchimeric phenotypes that can manipulate maternal tissues. We use cooperation and conflict theory to generate testable predictions about domains in which fetal microchimerism may enhance maternal health and those in which (...) it may be detrimental. This framework suggests that fetal cells may function both to contribute to maternal somatic maintenance (e.g. wound healing) and to manipulate maternal physiology to enhance resource transmission to offspring (e.g. enhancing milk production). In this review, we use an evolutionary framework to make testable predictions about the role of fetal microchimerism in lactation, thyroid function, autoimmune disease, cancer and maternal emotional, and psychological health.Also watch the Video Abstract. (shrink)

Smartphone use changes the landscape of social interactions, including introducing new social dilemmas to daily life. The challenge of putting down one's smartphone is an example of a classic coordination problem from game theory: the stag hunt game. In a stag hunt game, there are two possible coordination points, one that involves big payoffs for both partners (e.g., working together to hunt large game like stag) and one that involves smaller payoffs for both partners (e.g., individually hunting small game like (...) rabbits) but is safer because it does not require that your partner choose that option as well. This is similar to the challenges of putting down smartphones to have a face‐to‐face interaction: you and your interaction partner might both prefer the higher payoff option of having a face‐to‐face interaction, but neither of you wants to put down your phone and risk not having anything to do in the meantime. It is also discussed how new technological innovations are changing the payoffs of face‐to‐face conversation versus side‐by‐side smartphone scrolling. Insights that come from applying game theory to this “social media dilemma” are discussed here and potential solutions that come out of a game theoretic analysis are offered. Also see the video abstract here https://youtu.be/9esL578zM‐E. (shrink)

To better understand risk management and mutual aid among American ranchers, we interviewed and mailed a survey to ranchers in Hidalgo County, New Mexico, and Cochise County, Arizona, focusing on two questions: When do ranchers expect repayment for the help they provide others? What determines ranchers’ degrees of involvement in networks of mutual aid, which they refer to as “neighboring”? When needs arise due to unpredictable events, such as injuries, most ranchers reported not expecting to be paid back for the (...) help they provide. When help is provided for something that follows a known schedule or that can be scheduled, such as branding, most ranchers did expect something in return for the help they provide. This pattern makes sense in light of computational modeling that shows that transfers to those in need without expectations of repayment pool risk more effectively than transfers that create debt. Ranchers reported helping other ranchers more often when they belonged to more religious and civic organizations, when they owned larger ranches, when they relied less on ranch vs. other income, and when they had more relatives in the area. Operators of midsize ranches reported helping other ranchers more frequently than did those on smaller and larger ranches. None of our independent variables predicted how many times ranchers reported receiving help from other ranchers. Although ranch culture in the American West is often characterized by an ethic of individualism and independence, our study suggests that this ethic stands alongside an ethic of mutual aid during times of need. (shrink)