The gods themselves had their own monarchy, with laws of succession similar to our own, and they built a global empire upon the Earth, with great cities, temples and monuments, and mighty nations established on several continents. They created mankind as a slave race to work on their farms and in their gold mines, among other things. The Sumerian legends are very clear: man was made to bear the yoke of the gods. Man was separate from the gods, like a domesticated animal, and there was a great cultural taboo amongst the gods against sharing any of their sacred information with humanity, even things such as writing and mathematics. These gods ruled directly over Egypt, Mesopotamia, and the Indus Valley, and their rule is recorded in the histories of all three civilizations.
At some point, it is told, some of the gods broke rank. This is again recorded in just about every culture on Earth that has a written or oral history of legends. Some of the gods, finding human females most appealing, intermarried with them (breaking, of course, a major taboo within their own culture), and creating a race of human/god hybrids.