We call such folks "the Early People", and know from that name they lived in caves and trees, had almost no tools, and fell victim many times to natural occurrences. The Early People’s language was not very much like ours. Their words were mainly grunts and other sounds along with lots of pointing and hand signals. As they progressed, their language contained many clicking sounds that also had meaning for them. We would have a hard time learning their language now, because it was so different.

The natural occurrences that affected the Early Humans attracted their attention in very forceful ways. Sometimes one member of a group would get eaten by a large animal, or be singled out to get struck by lightning, or just die for no apparent reason. When heavy rains would fall from the skies and cause floods upon the earth, or volcanoes erupted, lightning strikes would cause loud, scary thunder and sometimes set trees afire or kill someone; earthquakes would attack them with no warning, and sometimes avalanches and mud slides would send rocks hurling at them that seemed to intend harm; or a tree would fall over for no obvious reason and maybe cause someone to get hurt or killed, the Early People tried to guess the causes.

They knew the wind could be felt but not seen, and that it sometimes did things like stir up dust, blow things down, made their trees dance and caused fruit to fall. They also knew it got inside their bodies while they lived, and could not be observed to be doing so when one of them had died. The breath at his or her nostrils would no longer be there. They thought the wind might be responsible for all kinds of strange occurrences, and so they named the parts of it that might be the cause of things, "spirits".

The notion of spirits satisfied a lot of their need to explain things to each other, and they felt that now they had a way to understand the secret forces that made nature work. They tried to figure out ways to keep spirits from getting mad at them, and to figure out what they’d done wrong whenever natural events occurred. Some spirits did mean things no matter what the Early Humans did to appease them, and early humans learned the concept of good and bad. From that, they could also see how the idea could also apply to themselves, that people might do good things, or bad things, for no real reason at all. Maybe, they worried, that was because of the kind of wind they had breathed, that good or bad spirits had gotten inside of them.

Have you ever fallen down, and wondered from that why you never fall up? The Early Humans wondered about all the same things we do when we’re still children. They didn’t have schools to go to so they could learn the true answers to such questions, and so they had to figure out for themselves what kind of invisible stuff held them upon the face of the earth and prevented them from falling off. Maybe they wanted to walk upon the sky, and peer out through the holes in it at night, and see what kinds of worlds they could find by looking out to where the daylight had gone. They could never do that, no matter what they tried. Something invisible held them fast to the face of the earth.

After a while had passed, some of them realized that other spirits might exist that were even more invisible than the winds. One of those spirits might be what holds things down. Those could be the kinds of spirits that lived in trees and other plants, who obviously lived and died like the Early People, but never obviously breathed. It seemed like an astounding concept, the answer to all sorts of dilemmas, and the reason for why they most times failed in all their efforts to appease the spirits and keep them from getting angry. They had been directing their attentions to all the wrong things.

The invisible spirits seemed very powerful, even strong enough to keep the winds held down, or to make them blow hot or cold, to cause ice and water to fall from the skies, and to poke holes in the sky at night so they could see the lights beyond it. Shooting stars and comets would come from out of nowhere and threaten the Early Humans with their presence, apparently hurled at them by the invisible spirits who lived beyond the sky.

You've never heard of any gods like the ones in This World

The Early Humans grew very afraid of such powerful invisible spirits, and named them "gods" to show they were somehow different and more ferocious than the spirits who lived in the winds. The gods were obviously the spirits in charge of things. Gods became the explanation for the kinds of spirits who lived underground, where the winds could never go, and caused volcanoes to erupt, or the earth to quake, made rocks tumble down from the mountains, or uprooted trees, or reached down with a finger sometimes to stir up the winds and make a cyclone walk and dance, and destroy everything in its path. The gods were powerful, indeed.

The Early Humans could find evidence of the gods in all sorts of things, and the concept satisfied humanity’s need to know for thousands of years. In comparison to that, science’s discovery of the true causes for most things has been only very recent. For that reason, most humans still believe in the gods and spirits the Early Humans had guessed to be the causes of most things. Such people go to places with names like "church", "mosque", "synagogue", "temple" to hear more about the various kinds of gods they believe in, because such ideas still appeal to the emotional instincts of our basic animal nature that had caused us to create them.