Collecting huge datasets for analysis has since the beginning of time been a good way to find insights. Recently some theories about safety and longevity of cousin marriage are being challenged by the power of big data systems:
researchers suggest that people stopped marrying their fourth cousins not due to increased mobility between different regions, but because the practice became less socially acceptable
“Less socially acceptable” is another way of saying laws against it were being passed. According to the seminal book on this subject, by someone with the same name as me, mathematical modeling show how those laws against cousin marriage were based in prejudice, not science.
Forbidden Relatives challenges the belief – widely held in the United States – that legislation against marriage between first cousins is based on a biological risk to offspring. In fact, its author maintains, the U.S. prohibition against such unions originated largely because of the belief that it would promote more rapid assimilation of immigrants.
Immigrants were barred from continuing their historic practices, much in the same way prohibition of alcohol criminalized Germans for their breweries and Irish for having distilleries. Keep these reports and books in mind the next time someone says cousin marriage is a concern for human safety or longevity.