Interestingly enough, a native American coworker of mine (a highly educated guy with a graduate degree in economics) was explaining what some of the tribes believed. This fella was pretty highly ranked in his own tribe, the son of a chieftain of some sort that traced his lineage back about 500 years. At any rate, he explained to me that many native religions held that the Gods came from the heavens and created humanity as a slave race. Apparently this is a pretty common native belief.