Scholars studying the evolution of religion tend to agree on one point: that religious belief is an outgrowth of brain architecture that evolved during early human history. What they disagree about is why a tendency to believe evolved, whether it was because belief itself was adaptive or because it was just an evolutionary byproduct, a mere consequence of some other adaptation in the evolution of the human brain.
Darwinians who study physical evolution distinguish between traits that are themselves adaptive, and traits that are byproducts of adaptations.
In architecture, a spandrel can be neutral or it can be made functional. Building a staircase, for instance, creates a space underneath that is just a blank sort of triangle. But if you put a closet there, the space takes on a function, unrelated to the staircase’s but useful nonetheless. Either way, functional or nonfunctional, the space under the stairs is a spandrel, an unintended byproduct.
“Natural selection made the human brain big,” Gould wrote, “but most of our mental properties and potentials may be spandrels – that is, nonadaptive side consequences of building a device with such structural complexity.”
Is there something about the cognitive functioning of humans that makes us receptive to belief in a supernatural deity?
Hardships of early human life favored the evolution of certain cognitive tools, among them the ability to infer the presence of organisms that might do harm, to come up with causal narratives for natural events and to recognize that other people have minds of their own with their own beliefs, desires and intentions. Psychologists call these tools, respectively, agent detection, causal reasoning and theory of mind.
And these three tools seem to account for the belief in god. To a godless heathen like me, at least.