Journal of Evolution and Health: A joint publication of the Ancestral Health Society and the Society for Evolutionary Medicine and Health

The Ancestral Health (or Paleo) movement is a collection of people who apply an evolutionary perspective to improve their health through lifestyle changes (e.g., diet, physical actively, sleep). In 2013, a survey of this population revealed that its participants did not align with media stereotypes; in contrast, survey participants were predominantly white, female, and middle aged. Since diet and health trends change over time, the goal of this survey study was to collect data on the members of the movement and compare the survey responses from five years earlier. In addition, we surveyed people who have left the movement to determine why they left and if they follow a particular diet now. Broadly, we hypothesized that participant demographics would remain the same while lifestyle characteristics (i.e., how they participate in the movement) would change. The survey was distributed online through various platforms (social media, blog posts, and mailing lists). A total of 1506 (54% female) participants completed the survey and a majority (75%) were still a member of the movement. Overall, numerous participant responses differed from the 2013 survey (18 questions; p<0.05 for all). One of the main changes between survey years was a general aging of the participants as demonstrated by an increase in participant age, income, and education level. This suggests that the movement is not capturing new and/or younger individuals. Further, the main reason participants left the paleo movement was a change to a new specific diet (16%; two most reported diets: low-carbohydrate and ketogenic diet), although 39% of participants who left do not currently follow any particular diet. We conclude by hypothesizing reasons for the changes and potential implications for the future of the movement.

Posttraumatic stress disorder (PTSD) is a burdensome condition that has been made worse by the Covid-19 pandemic and that can lead to suicide, especially among childhood trauma victims, rape victims, military service members, and law enforcement. PTSD is thought to be an evolutionary mechanism that functions to promote survival by heightening the stress response in an anticipatory fashion, allowing the organism to react quickly to recurring stressors or threats, even when stressors or threats are not present in the immediate environment. Frequent and sudden activation of the stress response can be uncomfortable and deleterious to health. The mammalian dive response (MDR) is another evolutionary adaptation that functions to promote survival by conserving oxygen when submerged underwater, and like the stress response, it disrupts the homeostatic environment. However, the physiological reactions induced by the MDR include slowing of the heart rate, conservation of oxygen, and conservation of energy, while the fight or flight response has opposite physiological effects. I hypothesize that frequent activation of the MDR and its parasympathetic components might inhibit brain regions involved with stress, and condition neural circuitry to anticipate aquatic submersion stimuli, thereby reversing the sympathetic mechanisms involved in the fight or flight response and PTSD.