Are there any religions that share a common "ancestor" (for lack of a better term)?

Religions are tied strongly to language and migration. Study the most ancient languages, and they all share common symbolism and words. Follow the migration of people, and you'll find that people in regions most adjacent to each other will have the most similar beliefs, symbolism, and pantheons. You'll also find that the original words don't change much, but words are added to fit the new region.