Singular or Plural

A comment on a previous blog got me thinking about the number of creators. It seems probable to me that something or someone was involved in the building of the universe and life but was it just one being or many. Many early religions believed in a number of gods. While this may have been because they didn't have the information available to us today to make their decisions, there must have been some evidence for it for so many people to believe it. Even in the Bible there are references to the God of Israel being, "mightier than the other gods" inferring that they believed there was more than one god.
I can't think of strong support for either option. I don't know why there couldn't be many creators if there was one. There does seem to be differences in the "powers" needed for certain events which may indicate different creators involved at different points. For example, creating all of the matter and energy in the universe would be a more difficult task than manipulating the genetic code to create a new species. On the other hand, one creator could have used different amounts of power. I wonder why the number of gods in people's beliefs decreased over time? Was it just inconvenient to have to appease many?