It is assumed that these Gods developed in different ways as cultures separated and evolved. Thus, a god such as the Vedic Mitra appears in Persian form as Mithra and then later develops into the Roman empire as Mithras. Because Aryan texts are the oldest surviving evidence of early Indo-European speaking peoples it was assumed during the nineteenth century that they preserved aspects of Proto-Indo-European culture, before the dispersal of the Indo-European peoples across Europe and Asia. It was thus thought that Aryan gods could be linked to Celtic, Norse, Greek and Roman mythology. Many ethnologists hoped to unify all the pagan European mythologies into a primeval Aryan belief-system.
Many such thinkers believed that all the Aryan mythical systems began as forms of Sun worship. Such ideas, now largely neglected, influenced the emergence of New Age thinking about myth, and theories such as Jung's notion of a collective unconscious.