From being savage like, he evolved, and then came the time when he learnt how to hunt for food and how to grow crops? This saved a lot of time. He then started living in groups, doing farming and raising cattle, this way he had spare time when he had nothing to do at all. The empty mind! When your basic needs are met, what you do is you start thinking. However, man was born with this virtue, but the time factor made it visible. The leisure hours was devoted in socializing, recreating and other creative stuffs and things other than food, shelter and clothing.
Human became so powerful that they could now fight with higher animals like big cats, of course, with weapons and not bare handed. Now, he was becoming like a master at least to some extent, as he thought.
But there were things beyond his control - storm, rain, lightening and thunder, floods, diseases, and the most frightening of all - 'DEATH. He even managed to get away with others, but when it came to face the dying phenomenon, he was helpless and clueless too. Thus, other part of the brain became active where emotions work, where he has to deal with sorrow, pain, loneliness, fear, lust and like. Death made him realize that 'anything that has a beginning has an end too.'
With regards to the forces of nature as opposed to the death phenomenon, he finally accepted the fact that there was no way to avoid them.
The only thing you can do is to run away from their actual point of impact, yet he thought to trick these forces.
Once Osho said 'dog' has been the oldest friend and pet of man only because it had the smart understanding of man's psychology. It fed man's ego and tricked him with his waiving tail. Subconsciously, man developed this so-called dog's virtue. He started pleasing nature and its destroying forces by way of worship and offerings made as animal sacrifice. He believed that as long as he keeps them contended, they are not going to harm him. Instead, they would protect him and this gave rise to many superstitions, customs, rituals and religious practices.
As the time went by and man's evolution continued, gradually, he understood that nature's fury was not the real threat. But it was 'death' and he had no answer to that. Then, he came up with the concept of 'God.'