Is there a word for the human tendency to be religious?

Solution 1:

Consider superstitious:

Having or showing a belief in superstitions.
‘many superstitious beliefs and practices are connected with sneezing’
_Lexico

There have been some research that argues the tendency toward superstition is a survival trait, which argues that superstitions may have been rooted in pragmatism rather than philosophy:

The tendency to falsely link cause to effect – a superstition – is occasionally beneficial, says Kevin Foster, an evolutionary biologist at Harvard University.

For instance, a prehistoric human might associate rustling grass with the approach of a predator and hide. Most of the time, the wind will have caused the sound, but “if a group of lions is coming there’s a huge benefit to not being around,” Foster says.
_{New Scientist}