The development of belief in the metaphysical is easily explicable in an evolutionary context. It has to do with the tools that early humans developed to deal with the environment, like anything else.
It must be remembered that evolution and selection do not work on gross physical traits. For instance, it is reasonable to assume that early hunters found that throwing things at prey would be advantageous. The increased food for those who were good at it would provide a reproductive advantage. So, strong arms, good throwing movement mechanics and so forth would be selected for, but so would purely intellectual skills like being able to accurately predict trajectories so as to hit things more often.
How does this relate to mystic beliefs? I propose it is an out growth, a neutral effect, of another very useful skill. When early hominids were observing the world they would see that, for instance, group members sometimes became sick. They could further observe that whenever a certain plant was eaten (this is a highly simplified example) the sickness occurred. Those who were better at seeing the causal relationship would have a survival advantage.
The ability to determine causal relationships is very useful and confers many survival advantages. So, we as humans are evolved to be good at seeing causal relationships in the world around us. We are, in effect, trained by evolution (in a manner of speaking) to look for causality.
Humans are also evolved to look for and easily recognize human faces. Being able to quickly pick out our own kin and read expressions on faces is of clear advantage. The side effect of this is that we see faces all the time where they aren't, because humans are good at seeing and filling in familiar patterns. Faces seen in clouds or rock formations, like the so called face on Mars, are an example of this.
So, since seeing causal relations has been selected for, we, like when we see faces where there are none, see causal relations in nature where none actually exist. Especially when the causation is, at the time, unknowable, the evolved drive to seek and understand things spills over and a causation is invented. Humans find that satisfying.
We are also evolved to believe our elders, because the passing on of knowledge from generation to generation is essential to survival. That's why, when our elders tell us that the thunder is the wheels on Thor's chariot, our need to seek causation is fulfilled and the false causation is propagated.
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