Birth control means that atheism and even nominal Protestant Christianity could end up dying out by numbers, as artificial contraceptive use and planned parenthood sees fewer children born to those not professing or practicing a religion.
By contrast, births among Muslims are on the rise, with an average of 4.29 children born to Muslims in the US, compared with just 3.04 children on average to atheists in the US.
These are among the findings of a wide-ranging study carried out in America, which found that because religious groups preach against contraception, they tend to have more children than those who label themselves as atheists.
The study, published in the journal Evolutionary Psychological Science, surveyed more than 4,000 students in the US and Malaysia, who were asked about their beliefs and number of siblings.
In Malaysia, Muslim families had an average of 5.89 children. The second most fertile parents in Malaysia were Hindus with 4.01 children — but this was a small sample of only five students. Atheists living in Malaysia had an average of 3.67 children.
In the US, atheists had, on average, 3.04 children, closely followed by Protestant Christians in the US, with an average of 3.11. Catholics had 3.42 children, while US Muslims had the highest number — 4.29.
Following a four-page questionnaire, researchers found that within both countries, the most fertile group was Muslims. Although there are no laws against or for contraception, conservative Islamic leaders preach against birth control, which has made it difficult for people to get access to what they need for family planning. Traditionally, Catholics also believe artificial contraception is sinful.
The study also added to a body of evidence showing that, overall, religious belief is associated with greater compassion, social inclusiveness and greater motivation to engage in pro-social actions.