Below is a really interesting graphic which visually demonstrates how a groups of people draw their beliefs from where they are born and how the religions and cultures/practices adopted by each religion have changed and evolved over time… demonstrating one thing…. its all made up by man, its all chinese whispers and what you believe is largely dependant on where you were born,….. no surprises there then.
The Evolutionary Tree of Myth & Religions, v2.0, by Simon Davies, is an awesome look at how human belief has shifted over the course of history.