Once we had evolved the necessary brain architecture, we could "do" religion, brain scans indicate.
The research shows that, to interpret a god's intentions and feelings, we rely mainly on the same recently evolved brain regions that divine the feelings and intentions of other people.
"We're interested to find where in the brain belief systems are represented, particularly those that appear uniquely human," says lead researcher, Jordan Grafman of the US National Institute of Neurological Disorders and Stroke in Bethesda, Maryland.
The researchers found that such beliefs "light up" the areas of our brain which have evolved most recently, such as those involved in imagination, memory and "theory of mind" -- the recognition that other people and living things can have their own thoughts and intentions.
"They don't tell us about the existence of a higher order power like God," says Grafman. "They only address how the mind and brain work in tandem to allow us to have belief systems that guide our everyday actions." Core elements
In the study, the researchers gave 40 religious volunteers functional magnetic resonance imaging (fMRI) brain scans as they responded to statements reflecting three core elements of belief. For each statement, they had to say on a scale how much they agreed or disagreed. The volunteers were believers in monotheist religions such as Christianity, Islam and Judaism.
First, volunteers responded to statements about whether God intervenes in the world or not, such as "God is removed from the world".
Here, brain activity was focused mainly in the lateral frontal lobe regions of the brain where theory of mind takes shape, enabling us to interpret other people's intentions. The regions link to mirror neurons which enable us to empathise with other people.
Second, the volunteers mulled statements on God's emotional state, such as "God is wrathful". Again, and as the researchers predicted, the activated areas were those where theory of mind enables us to judge emotion in others, such as the medial temporal and frontal gyri.
Finally, the volunteers heard statements reflecting the abstract language and imagery of religion, such as "Jesus is the Son of God" or "God dictates celebrating the Sabbath", or "a resurrection will occur". Here, volunteers tapped into areas of the brain such as the right inferior temporal gyrus, which decodes metaphorical meaning and abstractedness. Recently evolved
Overall, the parts of the brain activated by the belief statements were those used for much more mundane, everyday interpretation of the world and the intentions of other people. Significantly, however, they also correspond with the parts of the brain that have evolved most recently, and which appear to which give humans more insight than other animals.
"Our results are unique in demonstrating that specific components of religious belief are mediated by well-known brain networks, and support contemporary psychological theories that ground religious belief within evolutionary adaptive cognitive functions," say the researchers.
"It's not surprising that religious beliefs engage mainly the theory-of-mind areas, as they are about virtual beings who are treated as having essentially human mental traits, just as characters in a novel or play are," comments Robin Dunbar, an anthropologist at the University of Oxford.
"But it nicely reinforces my claim that it is the higher orders of intentionality that are crucial in the development of fully fledged religion as we know it," says Dunbar.