“The earliest religions were centered on the spirits of the ancestors”
The very earliest religions were most probably centered on the spirits. That is Animism.
Animism believe that a spirit inhabit each (living & non-living) being. Beings are : frog, chimp, human, cloud, wind, forest, tree, river, etc
The interesting thing about Animism is that ALL BEINGS ARE AT THE SAME LEVEL. There is no hierarchy. It is a world of Equals. Beautiful, isn’t it ?
I guess that it is much later that the ancestors came into the picture as a separate important group. In Japan, the traditional religion is Animist : there are the frogs, trees, etc etc AND the cult of the ancestors.
Jean P. Ciron