Goa'uld

Description
The Goa'uld evolved on the planet P3X-888, where there are still populations of primitive Goa'uld.[9] Their original hosts were the Unas, also native to the planet. The Goa'uld largely abandoned P3X-888 after deciphering the Stargate, spreading throughout the galaxy and conquering other races. Eventually, the Goa'uld began to die out, until in the eighth or ninth millennium BC Ra discovered Earth and found ancient humans to be much more suitable hosts, due to the ease by which they can be repaired by Goa'uld technology. (Stargate (1994))

History
The Goa'uld ruled Earth for thousands of years, in the personae of gods from Earth's classical religions. It is never clarified however, whether the Goa'uld impersonate deities that already existed in human mythology or if they themselves were the origin of those deities. From the humans the Goa'uld engineered the Jaffa, to serve as soldiers and incubators for their young. They also transplanted humans from Earth throughout the galaxy via the Stargate network to serve as slaves and potential hosts.[8] Ra's rule over Earth came to an end with a rebellion in the third millennium BC, they had forgotten about Earth until the twentieth century. (Stargate (1994))