A Brief theory on Fertility, Race, and Culture,

Premise - People generally like to date and marry within their own race and culture, for reasons of sexual preference and compatibility

Premise - A racially and culturally diverse city or community will mean people are exposed to and meet fewer people of their own race and culture, and therefore fewer people of their own sexual preference and compatibility. This is because not only the fact that you can only know so many people (Dunbar's number), but different groups and people will all take up resources and space in a community - housing, schools, churches.

Conclusion - A racially and culturally diverse city or community will have a lower fertility rate, because people will interact less with people they are attracted to and compatible with

Conclusion - This partially explains self-sorting and segregation of communities

Conclusion - Over time, a people will become more racially and culturally homogenous, because of this preference, because of economic pressures, and because of social pressures and the inherent dynamics of community building