Things never seem to change all that much

The base existence of religion is food, via the basic concept of survival. The sacrifice of one for another ; the life of one animal to continue the life of yet another. Here is the whole center of the relationship of humanity and the gods. The sacrifice begins as a simple process of killing to eat. We eventually begin paying those in charge of existence. The blood payment to the god(s) is a share of the spoils to guarantee future collaboration and loyalty. Interestingly enough, blood is the one part in the whole of the animal that is wasted, spilt on the ground. Thus it is offered up to appease our guilt and fear. The ancient hunter would ask the spirit or essence of the killed beast for forgiveness. While (coercing it) telling it that he too shall die one day and be eaten. Of course this appeasement is done very much to avoid the anger of the animal and avoid suffering the revenge (haunting, bad luck) of the beast's soul.
From these roots of sacrifice we move into the direct exchange of life to save life. Human sacrifice becomes quite a wide spread and practiced method of acquiring the aid of the god(s). Human blood of course is the greatest offering a human can make. ( incidentally oaths were usually made with a blood seal). These human sacrifices would be transported into the lands of the god(s) and act as messengers and intermediates to the god(s). The living would thereafter pray and leave offerings to the newly sacrificed for communicating directly to the deity for them. Such as the Catholic saints do and Jesus Christ. It is via these conduits that prayers are brought to the attention of god.
This whole need to communicate and gain boons from the god(s) is quite simple. They were the local authorities of existence for our ancestors. Each god had his or her appointed department of expertise to manage. Interesting how the similarities of such pantheons reflect human governmental bureaucracy and humorous how bribery is the basic concept behind religious overings. Just like politics.