Pathogen Load And The Nature Of Ingroup Derogation: Evolution Of Ingroup Derogation Based On The Sexual Penna Model

Ingroup derogation is a preference and affinity for outgroup members over ingroup members which contradicts both expert and lay beliefs. From an evolutionary perspective, ingroup derogation should even be impossible to exist. From the perspective of disease threat management, researchers have proposed the hypothesis of evolutionary of ingroup degeneration, which suggest that ingroup degeneration is a psychological mechanism which human evolved in response to a particular disease threats, and then the hypothesis have been tested. However, these studies have only indirect data to support for the hypothesis, but no direct theoretical basis. In present study, we using computational modeling analysis based on the modified sexual Penna model to simulate the evolution of ingroup derogation in the condition that both ingroup and outgroup members can bring disease threat to individuals, which provide further test for the evolutionary of ingroup degeneration hypothesis.The results show that the differences of the pathogen load in different regions will affect the intergroup attitudes. When the disease load in different regions is similar( the pathogen load difference is less than 1.5,the special disease prevalence of difference region is less than 40% or the special disease mortality of difference region s is less than 6%), the people of the two regions will evolve ingroup bias; The differences of the pathogen load in different regions is big enough( the pathogen load difference is higher than 1.5,t the special disease prevalence of difference region is higher than 45% or the special disease mortality of difference region s is higher than 6.75%), the people in low pathogen load region will evolve ingroup bias, while the people in high pathogen load region will evolve ingroup derogation. In addition, the ingroup derogation degree related to the local pathogen load. The higher the pathogen load, the stronger ingroup derogation will show in population. This study shows that ingroup derogation does have the basis of evolution. It is the same with ingroup bias, it’s an adaptive psychological mechanism in order to adapt to specific disease.