Notions of gods arise in all human societies, from all powerful and all-knowing deities to simple forest spirits. A recent method of examining religious thought and behaviour links their ubiquity and the similarity of our beliefs to the ways in which human mental processes were adapted for survival in prehistoric times.
It rests on a couple of observations about human psychology. First, when an event happens, we tend to assume that a living thing caused it. In other words, we assume agency behind that event. If you think of the sorts of events that might have happened in prehistoric times, it's easy to see why a bias towards agency would be useful. A rustling of a bush or the snapping of a twig could be due to wind. But far better to assume it's a lion and run away.
The survivors who had this tendency to more readily ascribe agency to an event passed their genes down the generations, increasingly hard-wiring this way of making snap decisions into the brain. This is not something that people need to learn. It occurs quickly and automatically.
The second trait is about how we view others. While living together in a tribe would have had many advantages for survival in prehistoric times, getting along with everyone would not always have been easy. Comprehending others' behaviour requires you to understand their thoughts and beliefs, especially where these may be incorrect due to someone not knowing the full facts of a situation.
This is known as "theory of mind". This idea says that we automatically assume that there are reasons behind others' behaviour which we try to work out in order to better understand why they behave the way they do. Not having this ability has been proposed to underlie developmental disorders such as autism.
You may be wondering what these two hard-wired processes have to do with belief in gods. Imagine a pebble falling in the back of a cave. Our agency device tells us that someone caused that to happen. With nothing in evidence, could it be an invisible creature or a spirit? If so, why would it be sneaking around? To find out secrets about us or to discover if we are good or bad people?
Another example might be a volcanic eruption. In the absence of geological knowledge, our tribal ancestors' agency system would have ascribed this event to a person – but one that surely has superhuman ability. And why would they want to cause such destruction? Perhaps the eruption signified a punishment, perhaps because the tribe had not acted in accordance with the being's wishes.
Of ghosts and gods
These two very simplistic examples should help illustrate how these hard-wired mechanisms could lead to the beginnings of a belief in gods, as well as ghosts and other supernatural creatures. Our ancestors would have drawn conclusions about supernatural occurrences by fitting together these instincts towards agency and the theory of mind.
This even applies to the Abrahamic, all-knowing, all powerful god. He may seem very inhuman at first glance, but it has been shown that we reason about Him in a very human way. For example we depict Him helping one person before moving to the other side of the world to help someone else. Hard-wired reasoning processes helps explain how religious ideas are so durable, spreading across continents and down through generations.
Both these and other ancient instincts appear to be in evidence from observations of children. Very young children seem to show very accurate understanding of physical laws. For example they know that two solid objects cannot merge into one or that horses do not have metal gears inside them. Developmental psychologists have suggested that children are intuitive biologists, physicists and – using theory of mind – psychologists.
Concepts which violate these intuitive understandings seem to be more memorable than others. A rose that whispers in Latin violates an intuitive understanding that plants do not have minds or mouths and therefore cannot whisper in an ancient language – or any language for that matter.
It may be that violating an intuitive concept draws special attention and interest and therefore helps embed the idea in memory. Many religious stories contain concepts that seem to violate this special kind of intuition, such as a man walking on water or a burning bush that talks. These tales take advantage of this feature of memory to successfully propagate themselves and resist being forgotten.
Putting these ideas together is one way of explaining religious thought and behaviour. You could go further and suggest that, if these ideas are correct, religion is merely a by-product of mental processes operating in error.
But this assumes that religious/supernatural experiences are not true. If the human mind was to truly experience a god, then the theories of agency and mind and our memory for the counterintuitive would help us make sense of it. If that were to happen, the conclusions would not be in error at all.
Explore further: Belief in God associated with ability to 'mentalize'