As religious people tend to have more children, they are set to spread their ‘believers’ gene’ through society, a paper published in Proceedings of The Royal Society B suggests. Dr Robert Rowthorn, Emeritus Professor of Economics and a fellow of King’s College, claims that genetic predisposition to believe in God is increasing due to the higher rate of childbirth amongst traditional religious groups.

Dr Rowthorn’s paper is based on the idea that some people have a genetic tendency towards religious faith. This is not a new claim: studies suggest that genes contribute about 40% of a person’s inclination to believe in God. Research in 2005 found that genes are particularly influential in determining religious behaviour in adulthood, whereas parental religion becomes less important with age. It is generally presumed that these tendencies are based on a complicated pattern of inheritance involving many genes, but Dr Rowthorn discusses the transmission of a single ‘religiosity gene’, explaining that he used this simplification to make his research possible.

Rowthorn investigated the implications of the ‘fertility gap’: the large discrepancy between the average number of children produced by religious compared to non-religious families. "The more devout people are, the more children they are likely to have", he says, citing studies showing that adults attending a religious service more than once a week have an average of 2.5 children, whilst those who attend once a month have 2.01 and those who never attend have 1.67. "Sects such as the Amish, the Hutterites and Haredi (‘ultra-orthodox’) Jews have total fertility rates three to four times greater than the secular average".

If this discrepancy in birth rates continues, highly orthodox religious groups will one day become a majority, suggests Rowthorn. The numbers of Amish in the US have doubled in less than twenty years, and it is proposed that sustained growth would put the population at 7 million by the end of the century and 44 million by 2150

In addition, Rowthorn claims, some members of highly religious groups will ‘defect’ to secular society, thus increasing the proportion of their genes in the general population. "Provided a core of high-fertility sects continues to exist, they will transform the genetic composition of society through either internal growth or defection...There will be an increasing number of people with a genetic predisposition towards religion but who lead secular lives".

The paper goes on to hint about the way society could be changed by having an increased number of people carrying the faith genes. "The findings of [earlier researchers] suggest that a genetic predisposition towards religion is associated with obedience to authority and conservatism...the diffusion of religiosity genes into the rest of society should see an increase in the number of secular people who are genetically inclined towards such values." Rowthorn avoids expanding on this potentially controversial suggestion, however, claiming that it is beyond the scope of the research.