Robert Rowthorn, an economics professor at Cambridge University, said studies showed that more religious people tended to have more children.
This, coupled with the existence of a genetic predisposition in some towards belief, led him to speculate that religion could spread.
Writing in the journal Proceedings of the The Royal Society B, he cited a worldwide study showing that the more religious had more children.
If people in these groups only married within them, he said “ultra-high fertility groups would rapidly outgrow the rest of the population and soon become a majority”.
In practice, however, many tended to leave these sects or marry outside them and consequently have less children than they might have done.
Such “defections” would “slow down the spread of the religiousity gene” but not stop it, he reasoned.
“There will be an increasing number of people with a genetic predisposition towards religion but who lead secular lives.”