Robert Rowthorn, a professor emeritus of economics at Cambridge University, published a study that models population genetics scenarios based on the observation that religious individuals have, on average, higher fertility than non-religious individuals. In an extreme example, Rowthorn cites studies that show Amish and ultra-orthodox Jews have fertility rates 3 to 4 times higher than the secular average. Rowthorn goes on to build mathematical models that show how religiosity can spread throughout the population. From the paper’s abstract:
The paper considers the effect of religious defections [i.e., abandoning one’s religion] and exogamy [i.e., marrying outside one’s religious denomination or marrying a non-religious individual] on the religious and genetic composition of society. Defections reduce the ultimate share of the population with religious allegiance and slow down the spread of the religiosity gene. However, provided the fertility differential persists, and people with a religious allegiance mate mainly with people like themselves, the religiosity gene will eventually predominate despite a high rate of defection. This is an example of ‘cultural hitch-hiking’, whereby a gene spreads because it is able to hitch a ride with a high-fitness cultural practice.
This models assumes, of course, that there is some sort of genetic underpinning for religious belief or, as Rowthorn puts it “[b]elief in the supernatural, obedience to authority, and affinity for ceremony and ritual depend on genetically based features of the human brain.” Naturally, there is a lot of debate on the biological foundation of religious belief. A great place to start is Carl Zimmer’s review of Dean H. Hamer’s “The God Gene.”
What do you think? What are some of the problems inherent in this debate?