The human behavioural immune system is a product of cultural evolution

Dalmaijer, Edwin S.; Armstrong, Thomas

To avoid disease, humans show far greater contamination sensitivity and hygienic behaviour compared to our closest living relatives, likely due to our increased propensity to experience disgust. While contemporary theories argue disgust is a genetic adaptation, there is surprisingly little evidence to support this claim. Here, we simulated 100 000 years of evolution in human hunter-gatherers to test a wide variety of theoretical models. Our results indicate that natural selection for monogenic or polygenic pathogen-avoidance traits is plausible. However, the cultural inter-generational transmission of such traits operated more quickly in realistic scenarios, and continued to work even when artificially constrained. In the absence of reliable empirical data, our computational work supports the hypothesis that cultural evolution outpaced its biological counterpart to select health-improving behaviours that benefited survival. This study serves not only as evidence of cultural evolution of the behavioural immune system, but is also an illustration of emerging theories that paint cognitive mechanisms as socially transmitted rather than biologically hardwired functions.