If you have small groups of people that don't interact with others, they will have limited or nil religions. If they interact with other groups (think tribes) then you still have a larger population, albeit disbursed.

As long as you have intelligent beings, there will be speculation about the unknown. Only when there is a leadership structure, is there a need to have a pat answer to explain the ineffable. The easiest answer is a black box. Historically, the box is called $deity.

I don't think it any more genetic than general human nature. Which is kind of like saying herd animals tend to herd. It's just a tool. The Chinese had warlords; hundreds of gods, but who cared? Pray to the kitchen god, but watch out for the warlord. Different values based on the most likely way to survive.

Just my 0.02
Hugh