MarkA

It depends if you mean the god of the Old Testament or god as a human concept. As a human concept god(s) are universal. Indeed, the concept of supernatural forces impacting on our lives appears to be an evolutionary by-product that is pre-Homo Sapiens in origin.

Chimps have been observed exhibiting religious, or proto-religious, behaviour in the wild. Things like fetishism where an individual animal or a small group will fixate on an object like a particularly smooth river rock or when a thunderstorm is approaching and the chimps will run around screaming and defecating while shaking clenched fists at the sky, hurling their faeces into the sky and waving branches at the apparent source of the thunder and lightning. These reactions have been recognized as religious impulses.

Neanderthals buried their dead in a foetal position and decorated the bodies with ochre and beads etc. The results of this religious behaviour has been unearthed all across the range of Neanderthal occupation so it was a universal trait among them and not just an isolated group practicing the rituals.

The human propensity for the religious impulse appears to be hardwired into our brains. Since the god of the Old Testament is not hardwired into our brains it is difficult to see how an argument can be mounted that this is the one real god and all others are false. Indeed, the evidence would indicate that the religious impulse is a by-product of some other evolutionary advance and that it emerged either in the common ancestor of humans and chimps or, more unlikely, separately in the earliest chimps and humans.

In terms of the god of the Old Testament, it was really a process that most likely began in pre-literate times. With the region at the crossroads of many trade routes the population must have been exposed to lots of stories and concepts and the trade routes themselves carried stories from one centre of civilization to another. The early, native myths must have been influenced by their neighbours’ beliefs and certainly by those from Egypt and Mesopotamia.

Local sky gods, rain gods, sea gods, vegetation gods and others must have undergone subtle changes as new concepts or better stories were circulated. As for the Hebrew god and how it changed from a local deity to a more important, universal one the changes were incremental over time. Rather like the evolution of Mars in the Roman pantheon I surmise.

Mars was the local god par excellence and was originally responsible for everything from crops to livestock to general protection of the people, including success in war, and even in the prevention of disease and the fertility of the population. As the settlers on the Tiber grew in importance and came into contact with other more sophisticated cultures and myths they adopted these and the concept of Mars changed so that it resembled now the Greek and Etruscan concepts of a war god.

With Yahweh he appears to have undertaken the same metamorphosis but continued his development towards universality simply because the Hebrews were unsuccessful militarily and politically. They were continually under the domination of Egypt or some other power and so their god became separate because it could not be assimilated completely into one pantheon or another as the ruling state changed from one to another. Because the Hebrews were at the periphery of whatever empire they were subject to, they retained their identity but their concept of themselves as a separate people could not lead to an integration of their local, particular god into another pantheon.

DrZoidberg

Wasn't the first Christian notion of God, monotheism, the theory of the Unmoved Mover? A solution to Plato's problem of where his moral absolutes came from. Plato assumed we had moral absolutes but didn't manage to figure out where they came from.