(PhysOrg.com) -- In the past 20 years, the Amish population in the US has doubled, increasing from 123,000 in 1991 to 249,000 in 2010. The huge growth stems almost entirely from the religious culture’s high fertility rate, which is about 6 children per woman, on average. At this rate, the Amish population will reach 7 million by 2100 and 44 million by 2150. On the other hand, the growth may not continue if future generations of Amish choose to defect from the religion and if secular influences reduce the birth rate. In a new study, Robert Rowthorn, emeritus professor of economics at Cambridge University, has looked at the broader picture underlying this particular example: how will the high fertility rates of religious people throughout the world affect the future of human genetic evolution, and therefore the biological makeup of society.
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Rowthorn has developed a model that shows that the genetic components that predispose a person toward religion are currently “hitchhiking” on the back of the religious cultural practice of high fertility rates. Even if some of the people who are born to religious parents defect from religion and become secular, the religious genes they carry (which encompass other personality traits, such as obedience and conservativism) will still spread throughout society, according to the model’s numerical simulations.