MOST people who are devoutly religious or determinedly atheist believe they've examined the evidence, researched correctly and come to their own conclusions about how the world works.
However, psychologists are now coming to realise you might have less control over this process than you think.
University of the Sunshine Coast Senior lecturer in psychology Rachael Sharman said levels of religiosity - how susceptible you are to embracing religion, rejecting it or falling somewhere in the middle - is actually a genetic trait.
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"For reasons we don't entirely understand, some people seem very predisposed to either being very religious or not at all and in fact, the research tells us that's highly genetic," she said.
That's not to say your genetics decide whether you're Catholic or Muslim but how deeply you embrace whichever faith or spiritual philosophy you identify with.
Ms Sharman said researchers have used twin studies to exclude environmental effects, such as one's upbringing, social networks or external tragedies.
"Identical twins share 100% of their DNA and non-identical twins share 50%," she said.
"By analysing twins, they've found quite conclusively religiosity is a genetic trait.
"Even in identical twins separated at birth with quite different belief systems end up with the same level of religiosity whether on one end of the world or the other."
This genetic link was discovered by accident, according to Ms Sharman.
She said researchers in the United States of America were analysing links between genetics and alcoholism, and found the revealing data amongst groups which didn't drink due to their religion.
"Someone finally decided to analyse that data and it's now been replicated all over the world," she said.
In some studies, this genetic phenomenon has been linked to the individual's "existential uncertainty", meaning one's level of religiosity would naturally depend on how unsure or anxious a person is about their existence.
One 2013 twin study in particular also indicated with this being the case, religion may not be the only social system which could fulfil our innate human need for existential meaning.
Gary Lewis and Timothy Bates wrote, "It might be predicted, then, that under certain conditions, even a secular apparatus, should it be able to meet the community and existential needs of people, may be attributed the same importance in people's lives as religion often occupies."
A separate 2008 study concluded biological predispositions seemed to have most effect when there was more opportunities for free-thinking, meaning those raised within strict religious or non-religious environments were less likely to have their genetics responsible for choosing their faith than their more independent peers.
The researchers also found genetics were more likely to play a stronger role in adult decision-making regarding religion than in children or adolescence.
Ms Sharman said it was natural for social and existential factors to all play a role, but emphasised all the research she's encountered with twin studies highly indicates a genetic factor in determining individual religiosity.
"So before you go thinking you're very clever that you've decided on one way or another, remember that it's all in your genes," she said.
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